Who has been the Doctor's companion for the longest time?

I was having a debate with my brother the other day, about this question. He claims Clara is the longest time companion because she helped every incarnation of the Doctor. (little spoiler from Series 8):

Even since his childhood, as we witnessed in "LISTEN"

That can't be right because those were Clara's echoes for the most part. My counter answer: Handles, the Cyberman head we met in The Time of The Doctor.

The Doctor got stranded in Trenzalore for 300 years, waiting for the TARDIS to come back after returning Clara home. During that time, he probably saw three or four generations of Trenzalorians (is that word right?) live their full lives, but Handles remained by his side after finally breaking down when the TARDIS and Clara returned 300 years later.

I'm not very familiar with Classic Who. It's been impossible for us to get access to those episodes here in my country. Is there a companion for the Doctor who travelled with him for more than 300 years? My first guess was Susan, but I can't find information on how long they travelled after leaving Gallifrey.

TL;DR: Well, the title. Does Handles have the record for being with the Doctor for the most time?

Answer

Record-holders for longest tenures can be measured in different ways.

1. All time winner: The TARDIS, as a sentient being, she wins having been with the Doctor since the character's creation with the exception of a period of exile on Earth.


2. Consecutive episodes: Jamie McCrimmon - 113 episodes, the better part of three seasons.


3. In terms of stories: Amy Pond from the start of Season 5 to midway through Season 7.


4. In terms of calendar time: Tegan (3 days shy of three years), followed closely by Sarah Jane (six weeks shy of three years). Both are the only travelling companions to appear during four consecutive seasons as a show regular.


5. Long term regular cast member: The Brigadier showed up for five years during Jon Pertwee's Doctor Who. Regular or not, the character appeared in more episodes of the programme than all of the 1980s Doctors except Tom Baker.


6. In terms of continuous story time: Handles, having spent 300 years with him on Trenzalore, before finally succumbing to breakdown.



7. Longest time span of time between first and last adventures from the Companion's POV: Currently goes to Rory Williams aka Rory Pond or The Lone Centurion who waited a long 1894 years for the Pandorica to open and release his beloved Amy Pond before continuing on his adventures with the Doctor and rebooting the Universe - Second Series Doctor Who.

From the TARDIS Wiki entry on Companions

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  If the Doctor's TARDIS is considered as a companion, she tops all categories, having been a constant in the series since 23rd November 1963 and being ubiquitous across all media with the notable exception of the early Third Doctor era when the TARDIS was not featured regularly due to the Doctor's exile to Earth, as well as the Fourth Doctor stories The Sontaran Experiment and Genesis of the Daleks and the Tenth Doctor story Midnight.

  
  


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  In terms of consecutive individual episodes, Jamie McCrimmon is the easy winner with one hundred and thirteen episodes between TV: The Highlanders and The War Games, outdistancing most Doctors, much less all other companions. He served for the better part of three seasons, during which Doctor Who had its highest episode count. Due to changed television consumption habits, that record will almost certainly never be approached, much less broken.

  
  
  


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  In terms of stories, given that BBC Wales has a much higher story count than the original series, the high water mark has so far been set by Amy Pond, having been the primary companion for 31 full-length televised stories from the start of series 5 to her departure midway through series 7. In addition, she has cameo appearances in TV: Closing Time (where her name does still appear in the main credits) and TV: The Doctor, the Widow and the Wardrobe.

  
  


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  In terms of calendar time that the public would have perceived a character as being a regular on Doctor Who, the winner is Tegan. She clocks in at three days shy of three years, from her first to last regular appearances. She only very narrowly defeats Sarah Jane, who is some six weeks shy of three years as a regular character. Note that calendar years are not the same thing as seasons, because Doctor Who did not begin its seasons on the same date each year (it should be noted, however, that Tegan and Sarah Jane are as of 2012 the only travelling companions to appear during four consecutive seasons as a regular).

  
  


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  Special mention should be given here, too, to the character of the Brigadier. It's entirely possible that some members of the viewing community regarded him as at least a kind of regular throughout all five seasons of Jon Pertwee's Doctor Who. Although this isn't true from a contractual standpoint, he's still an incredibly long-serving member of the cast. Regular or not, the character appeared in more episodes of the programme than all of the 1980s Doctors except Tom Baker.

  
  



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  In terms of how long a companion has remained with the Doctor continuously within the story, Handles likely holds the current record, having spent 300 years with him on Trenzalore, before finally succumbing to breakdown.