PAL 101:

Passive losses are limited to passive income.

If AGI is low enough, passive losses from a real estate rental might be deductible up to $25,000.

Suspended passive losses get freed up when the activity is disposed of in a fully taxable transaction.  So quite often I see several years of suspended losses, followed by a big loss allowed in the same year that there is a capital gain on the sale of the real estate (I have one that came in Sunday that I haven't looked at yet!)