Start your travels closer to home.....circling out away, as time goes on, so that she becomes used to longer and longer spells without you near by.
I would think, that your mother would really not want you to ruin your lives because of her...and while that is a bit of an exaggeration, that is what she is asking. You yourself said that it may very well be that you only have the next couple of years, and that you won't be living until you and DH are in your 90's....and of course, you wouldn't be traveling as much then either.
Depending on your RV, and your abilities, you may even want to take Mom on a trip with you for a week or so, to show her what you are doing.
Good luck.....and I, like everyone else, suggest you live your own lives, and hit the road! Guilt is brutal, but it's not a real chain that can hold you to your house!
