From the 2008 F&G Book:
"The preference point system is designed to award a point for each unsuccessful draw attempt in a hard-to-draw area for individuals who elect the preference point option and remit the additional preference point fees, yet not penalize those who wish to list an easier to draw area on their second or third choice. If a person draws on the second or third choice when electing the preference point option, a preference point will be awarded even tho a license is issued. If the person is successful in drawing his or her first choice, then all preference points are deleted but the preference point fee paid for that year is refunded. DRAWING A SECOND OR THIRD CHOICE DOES NOT CAUSE PREFERENCE POINTS TO BE DELETED." Their bold print, not mine.
I burned my mule deer and antelope preference points last year in a general area, but am still accumulating the elk points. We thought about going this year, but with the economy, we are just going to purchase points. We've accumulated a point for every year that they've been available, so I assume that when we decide to go we should have a very good chance of getting what we put in for.
If you skip a year in applying for points, your points won't be lost, but you can't skip 2 years in a row.