I guess I'll show my age by mentioning that in my youth, my favorites were "Bringing up Father" (featuring Jiggs and Maggie) and "Our Boarding House" (featuring the inimitable Major Hoople [Fap!]). These (especially BUF) ran for ages -- BUF began running, I think, about 1920 and finally disappeared in sometime in the '70s. It never changed. Jiggs and Maggie started out as middle aged and stayed that way for 70 years.
On the other hand, in Gasoline Alley (running since the '20s), the characters age. Walt Wallet is now pictured as about 100, recently widowed, and I presume will finally shuffle off this mortal coil sometime in the next few years. Skeezix, who was a baby in the original strip, is now retired and in his 70s.
Another oldie which as been subjected to PC treatment is "Snuffie Smith". He was originally a minor character in "Barney Google" [with the Goog-goog-googely eyes] and about 40 or 50 years ago morphed took over the strip with very rare appearances by Barney. He was a shif'less good-fer-nuthin moonshining varmint who was kept alive by Loweezy, his long-suffering wife. But several years ago, he reformed -- gave up moonshining and chicken stealing, treats "Maw" like a human being and being a father to his infant and nephew. Still stuck in time, however; Tater, the infant, has been an infant for at least a generation.
Interesting how some long-running strips evolve, others are stuck in time. Doonesbury (my not-to-be-missed favorite) has kept up with time. All the characters have aged with the exception of Zonker, who is a world unto himself.
