I've had several mechanics say to me over the many years that to extend the life of a vehicle you need to address the fluids as they do wear out. Fuel additive -- for Pete's sake, that is a bottle of Seafoam that costs $7, do it yourself. It should be done every 10K miles. I have to agree about the tranny flush, just empty the oil and pan (where you can see if any metal is at the bottom) and add new VS doing a "flush". You can do a PS flush yourself, buy a bottle of PS reconditioner, and empty the fluid and refill with new. So what does servicing the differentials really mean? Topping them off? Or draining them and refill with new fluid? No opinion on the transfer lube. Oil changes--I assume you are using synthetic if going 10k, but what about the oil filter? Many are only good for 5k and need to be replaced every 5k. Some totally miss this. Another thing over looked is chassis lube. That needs to be done every 10k too (ball joints, u joints, etc). SAVE all your records with receipts and place into a file for that vehicle. (Each vehicle should have it own file.) When it comes time to sell - you can prove that you did the service work, and thus get more $ on resale. There is a fair amount of peace of mind for potential buyers who are wondering is anything was ever done VS done as scheduled and are willing to pay more for it as a result. And as mentioned already you should get a lot more life out of your vehicle if the fluids are indeed changed on a regular basis. Look for a good mechanic that does side jobs on the weekends that charges say $30-50 an hr VS the $90-120 that a full service shop does. Have him do the things that are above your skill set and cut the bill by over a 1/3 if not by 1/2.