How do you guys deal with annoying tenants?

[Bin Chen]

Hi everyone, 
I am having an issue with an annoying tenant that complains about everything. He pays his rent on time every month but complains about every little thing.  For instance before he moved in he complained that there was a lot of dust all over the house and asked me to hire a cleaner.  Shortly after he complained about the gap between the floor and his door and how cold air escapes from his air conditioned room through that gap. He even complains about things like using a little extra force to slide the shower door.  
I have been more than cooperative with resolving all these issues since they are minor.  This time he's complaining about the insulation in the house  and how he has to set his thermostat to 75 to get it to heat up to 70. From my understanding replacing the insulation in his apartment would cost a lot of money.  It's not that the heat isn't working so I'm not sure how to deal with him. 

Has anyone had a similar experience and how did you guys deal with it?  Thank you