I purchased a service plan when we purchased the RV. Was pricey but was for 7 years coverage. I am not mechanically inclined and so do repairs with the checkbook............
So far I have been covered for a failed alternator, cracked brake calipers (not covered by the WH recall), failed converter and several other smaller items. My deductible has been only $50 per repair. I am well ahead of what I paid for the coverage and I have had seven years of less worry. I also have a good roadside assistance program which saved me from a $2000+ flat bed tow in Alaska years ago!
For me, I need the peace of mind that any major repairs are covered. I understand that for some people it is a bad bet. For me, it has given me peace of mind and protection from unexpected large repair bills. Mine will expire soon and I will be looking closely at Good Sam as a possible replacement coverage.