I used to keep a list, but it hasn't been updated in years( I need to do that before I forget names). I do remember being the most proud around age 28 because I'd finally "made my age." I was close a few times before, but I'd get in a relationship and age another year without an additional new lay.
Throughout my life, It's these relationships that I've had... that keep the numbers from going higher. I don't count oral, but if I did and also counted former women that I recycled months or years later, I'm sure that it would hover around or be over the 100 count.
As to the burn-out, yes... it definitely occurs. It's like watching your favorite TV show and you've seen all the episodes. It's still fun, but it usually doesn't seem as 'new' because you can catch yourself going on auto-pilot because you already know how it'll usually play out.
In fact, I've caught myself becoming lazy. I have two former Girlfriends that will invite me over after work for drinks or a home cooked meal; which eventually leads to their bedroom. It's satisfying enough, but I look at this as just a step above self-pleasuring. I never stay over night because I don't want them getting comfortable with an over night routine. About once a month, I'll meet someone new. Sometimes things happen and sometimes it doesn't. If I didn't have two "back ups" and a lot of previous encounters, I'm pretty sure that I'd be more motivated.
