If your injectors have never been checked out to your knowledge maybe its about time. Also to check chain stretch and set pump timing is a requirement as well to maximise power anyways with a 240d. As I have stated many times before you want all the power that engine can deliver.

Plus check the valve clearances every 15k makes sense. Also a compression check might not be a bad ideal to make sure the engine has some sembalance of balanced firing. Although a lot of 240ds owners used to report milage of about 24 in many cases and you are using the air conditioner almost continually. You will never know otherwise if the milage can be higher until you do what is fundementally a good tune up.