I tip extra if someone goes above and beyond what they are paid to do and usually tipped to do.
If my towels are changed more than twice a day and my bed is remade during the day after I've napped in it and have gone out again, when my waiter goes above and beyond his normal duties I tip extra.
First find out what they are SUPPOSED to do and how often they are SUPPOSED to do it. If it's less than what the policy states it should be...you can adjust your tips down...if it's MORE than what they're SUPPOSED to do, I tip more than the standard amount.
Basically, it's how YOU feel you are being served and what it's worth to YOU.
Some people think the staff is there to serve their every whim...not so...they have a certain criteria to fullfill...if it's filled...they deserve what the tipping is suggested to be. If it's MORE than fullfilled...they deserve more.
Just remember, they're not your slaves and if they just do their job and aren't willing to be your slave, that doesn't mean they don't deserve the suggested tip.