He first claimed the jersey after winning the eighth stage of the 2013 Tour and it has rarely been off his shoulders since.
He wore it for 14 days in 2013, 16 in 2015 and 14 again last year, before taking it six days ago.
He's now up to joint fourth overall in the all-time list, level with five-time Tour winner Jacques Anquetil.
"It would certainly be sweeter if I am able to keep it all the way to Paris," quipped Froome.
"I was just told that once I crossed the line -- the 50th day in yellow, equal with Jacques Anquetil.
"It's a huge, huge honour."
If he does keep it all the way to Paris he will go past third placed Miguel Indurain, who held it for 60 days.
But he would need at least another Tour to reach Bernard Hinault's mark of 75, and two more to match Eddy Merckx's record of 96.
But all four of those riders are five-time Tour winners and with three already, Froome is well on his way to matching them as he leads this year's race by 18 seconds from Fabio Aru.
'Very clever'
The Italian won last Wednesday's fifth stage and Froome admits to have been impressed with his tactical nous.
"His biggest strength was on the Planche des Belles Filles where tactically he made a very good move at the right moment," said the 32-year-old Briton.
"Given also the profile of the last few kilometres (of the climb) there was a flat part before the final where the main GC guys did ease up and no-one wanted to pull on that part.
"It was tactically very clever; he went on to win the stage, so tactically he seems to read the race well.
"It's something I'll have to be attentive of going forward."
Aru and his Astana team-mate Jakob Fuglsang are both well paced in the overall standings (GC), in second and fifth, and Froome is wary about the threat their tandem could pose.
They worked well together at last month's Criterium du Dauphine, which Fuglsang won, and did so again on Sunday's stage as they both made GC gains.
"Astana have certainly got numbers up there with Jakob Fuglsang, and Fabio in second place. It could be the card they play, but we're ready for that," said the Sky team leader.
"I've also got Mikel Landa in the top 10 (ninth) on GC and that could be the card for us to play in these days.
"I think they'll work together, as we saw on the descent off Mont du Chat the other day.
"Once we got down from there, they both committed to trying to catch (Romain) Bardet, which was intelligent riding from them as well because Bardet is a threat to all our positions.
"(Fuglsang) is really strong, of course he won the Dauphine and has shown already he's in great shape.
"He's not far off, just over a minute down (1:37), if he attacks I have to go after him, it's as simple as that."
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