I did extensive plastering of cracks, etc, repainting, sanding wood floors, new bedroom laminate floors, and new bathroom.  

If we have to repaint, my painter can go in there with a sprayer or roller and repaint the whole thing in a day.  

Yeah,you really can't do big rehab jobs like reroofing with tenants occupying the property.I would definitely give them notice to move in 30 days and tell them when the property will be available again and what the new higher rent will be.Doubtful they will apply to return the property with the higher rent and you will be able to screen newer and better tenants.You should also repaint,carpeting,tile the kitchen,new appliances( Memorial Day Sales!)

We have always allowed tenants to repaint the walls as along as they return the paint color back (in a professional manner) to our original colors by move-out time.This policy hasn't worked out too well for us we have had to spend too much time and $$ repainting walls and trim for the tenants that didn't get around to returning the colors back and/or fixing what their version of professional painting is.I'm thinking along the lines of not allowing any tenant repainting of our properties unless it is contracted directly through us and putting a penalty of something like $300-$400 per room for any unauthorized tenant painting that is done.I'd appreciate any recommendations.

In the time that I have owned it, they have asked me to spackle and repaint rooms, fix doors, etc.

A hot water heater one year, a HVAC unit one year, repainting parking lot one year, that sort of thing. 

Costs to clean and repaint, etc., in-between guests?

Lets see if the checks keep coming but in the meantime this is found money and he has paid just under a third of the bill for completely repainting the unit.

Maybe a different color in the bathroom if you will use a higher gloss paint.You want to minimize how much paint you have around, make it easy to repaint as needed, and spend less time switching colors.  

I prefer flat because it's easier to apply. 99 times out of 100 you're going to have/want to repaint a unit when someone moves out anyways.