I’m wailing in sadness here knowing that I can’t ever be you, early forties and reading Pratchett for the first time in my life. Alas.
Otherwise no regrets reading him 25 years ago, none at all.
Re-reading deep books when you're older is also a joy: You've forgotten a lot, and you appreciate different things.
The Minas Tirith part of the ending of LOTR hits hard as a 50-year-old man, but as a kid, it was just a lot of pomp.
Hope you get a good reread sometime.