As a semi-reformed 'Achievement Ho', I'd like to say I totally don't care about the answer to that question, but I sort of do! Xbox 360 Achievements has a story claiming that Microsoft is about to up the points limit of achievements to 400 for some games, and I think I'm in favour.
According to its source, this will be the new rules for XBLA games.
Base: 400 Gamerscore / Max of 30 Achievements DLC: Up to 100 Gamerscore + 8 Achievements per Quarter (4 Max) Total: Up to 800 Gamerscore / 62 Achievements
Although I'd love to take the high ground here and say it completely doesn't matter, there have been times when I've invested time in a game, just to get achievements, and I've often felt that XBLA games got the crappy end of the stick in this regard. Some games, like Trials HD, for example, have hours and hours of content to plough through, but the achievement list really doesn't reflect that. I'm sure that had resulted in some folks spending less time with the game than they would have.
Still, it's an economy like any other. You can't tinker too much lest the points themselves become worthless. That's the nature of gamification. If it's not managed correctly it loses all value and becomes more of a hindrance than anything.
XBLA Achievement Policy Change Coming Soon [Xbox 360 Achievements]