If you got away with only $260 for what most of us pay $350-$500 for annual service, that's good. Best to use CAT authorized service provider, which you did; he will use the best parts and fluids. Yes, annual service is a built-in expense of ownership, for any diesel. You should budget for something to go haywire frequently, since these coaches are loaded with complicated parts and devices; there's always something that needs attention or repair.
Our coach hasn't been on the road for 19 months, so I expect there will be consequences to that - just hope we can afford them, and they don't ruin our next trip. When nothing goes wrong, and we can afford to, we both enormously love using our coach.
-Joel