Most people hit walls along the way, rather than improving steadily. You'll improve a few hundred rating points, then get stuck for a while at a plateau, and it'll take you a while to work through it. When you do get past the plateau, maybe you'll increase another 200-300 points pretty quickly before hitting the next plateau. And as others have stated, rating improvements are tougher the higher you get.

For instance, the first time I was in USCF, my rating got stuck in the low 1400's for about a year. Then I stopped playing, and when I came back last year, my rating dropped a little, and I got stuck in the 1300's for the second half of last year. But I broke through that wall at the start of this year, and my rating is now 1552 and rising steadily. Based on recent performances, I seem to be going roughly 50% in games against opponents rated 1650-1730, so I figure my rating should catch up to that increase in playing strength shortly. But it wouldn't surprise me if I hit 1700 within a month, then next summer, you'll see me whining here about being stuck at 1700 for an entire year and not knowing how to break past that plateau.

--Fromper