We haven't yet purchased our TT but will be in the next few years , right now it's all about the research . There seems to be lots of discussions regarding folks changing out tires and/or axles and/or...
I owned a pop-up for 3 years, a hybrid for 5, and a large travel trailer for 5 more. I did not need add'l ground clearance so no axle swap for me. I never had trouble with tires (kept 'em inflated and I checked for wear). I did install shocks on the last trailer due to our awesome roads.
I don't believe that you automatically need to swap out the entire suspension. Use it for a while and see if it's needed.