Hiya.
Still playing my 1e AD&D character from 1980. Not all the time, of course, but when I do play (and not DM) 1e, it's Denakhan. He's now about half-way to 21st level as a Magic-User (a grey elf; he actually started 'life' as a 'regular Elf' in Basic D&D back in '80). Anyway, when I was playing consistently with my original group, we played about 12 to 20 hours per week (ahhh...the freedom of youth!

). This lasted about 6 years where he *just* crested 20th. Since then (maybe 1989 or so), he's garnered, perhaps, 110,000xp...but I only get to play him every few years.
For those wondering about XP in 1e... Gary figured it would take an average group of about 6 (iirc) characters about a year or two to hit 9th level. Then gain another level every year of play thereafter. I think this was assuming a 6 to 8 hour session, once a week. So...the guys with the 15th level characters are definitly on the "slow" side of leveling. Assuming they are playing 16 hours per month, (about half 'normal' 1e AD&D playing base assumption in my experience), we have levels of about 20 to 22...not that much above 15th.
In my 1e AD&D campaign I just started, everyone is still 1st level, with the thief character being the only one who is 2nd. We've played about 4 hours every week for two months or so. Although they *did* just succeed in killing not one, but *two* manticores down on the 4th level of the dungeon...so that should crest all of them to 2nd level tomorrow (Sunday). I figure, at this rate, they should probably hit level 7 to 9 by the end of the year. Maybe.
^_^
Paul L. Ming