Here are the age differences between the last screen appearance of one Doctor and the first appearance of the next (going by airdate, not production date, so some may be a bit high):
"The Tenth Planet": Hartnell: 58 / Troughton: 46
"The War Games"/"Spearhead from Space": Troughton: 49 / Pertwee: 50
"Planet of the Spiders": Pertwee: 54 / T. Baker: 40
"Logopolis": T. Baker: 47 / Davison: 29
"The Caves of Androzani": Davison: 32 / C. Baker: 40
"The Ultimate Foe"/"Time and the Rani": C. Baker: 43 / McCoy: 44
(movie): McCoy: 52 / McGann: 36
/"Rose": McGann: 36 / Eccleston: 41
"The Parting of the Ways": Eccleston: 41 / Tennant: 34
"The End of Time": Tennant: 38 / Smith: 27
So you're technically right about the sequence, Starkers
, but McCoy is actually 2 1/2 months younger
than Colin Baker; it's just that there was a gap of 10 months between Baker's last appearance and McCoy's first. If Baker had returned for his regeneration sequence, they would've both been 44. And Pertwee was only 8 1/2 months older than Troughton. So I'd say there were two cases where successive Doctors were approximately the same age. Not to mention that McGann is 4 years older than Eccleston in real life; it's just that there's a huge gap between their respective appearances.
All in all, I'd say the only substantial upward jump in age was from the Fifth Doctor to the Sixth; all the others regenerations either made the Doctor younger (more than a decade younger in five cases) or kept him approximately the same age.