Tim,
I have a Fleetwood Excursion, and I had a problem with the largest slide being very slow to come back in. I took it to the dealer, who replaced the motor, saying that it was about to fail completely.
Are your slides electric or hydraulic? If electric, I would get the motors checked out. If hydraulic, you may have a low fluid level.
Unfortunately, the dealer I got mine from is out of business, so I hope I don't have any more problems!
JT