In the old days, when D1 was the new game online, I got an MP rogue to lvl 50, and eventually a mage too. I didn't think it was that big a feat at the time, but playing some now, I can't believe how many games/hours/months that must have taken me.
I've been playing an MP rogue in Hellfire for a few months now, and she got up to the mid 30s fairly easily. Even up to 39 or so was pretty quick, since I played in mini-mage mode and did a lot of clears of the cats, while hunting for Enchanted shrines. Good experience in the cats until about level 40, and the monsters are weaker and lack resistances, so chain lightning and some fireball can just cleanse them. Goat shrines + CL = FTW!!!1!
Since I got past 40 though, the leveling progress has evaporated. I've not kept count, but i've played 2 or 3 games a week for the past couple of months, usually a full or nearly full clear of 13-16, and I'm maybe lvl 42.5 now. I remember in the old B.net days most players were lvl 40, 41, maybe 42. And now I see why; you have to put in some serious hours, doing repeated games of hell/hell, to level up any further.
According to Jarulf's Guide, you need to make about 7400 kills to go from 42 to 43, at the max experience (200 x clvl = 8400 @ lvl 42). There are around 180 monsters per level. So quick math: 7400 / 180 = 41 levels. If I do a full clear on 13-16, that's 10 games. I'm not going to dispute that, but damn it seems like more than that. I guess it's because I'm playing 2-3 games a week, so it takes me a month for one level. It'll take me 10,345 kills to go from 43 to 44, or 57.5 full clear Hell levels. Whee.
It's harder to find the interest for it now, since there's no magic find, and since there aren't top level elites and runes and other ultra rare things to try to find. It's Hellfire so I've had optimal equipment for a long time, and I've found every unique I want with this rogue (dreamflange, royal circlet, t cap), and while I can still much improve my jewelry, it's not worth playing many games just to try to find jewelry. So I only play when I want to play, and as long as I'm enjoying playing. No dedication!
I hope no one is so bereft of other meaningful activities these days that they'd play that much D1, but I'm curious if anyone is?
Update: I made a table showing all the level up rates, experience required, levels to clear, etc.