When I had Uk built vans I changed about every 4 years as things were starting to get loose - particularly furniture made of veneered chipboard. Nothing much you could do about it, as nothing sufficiently solid to lever against to re-position. Current Brustner has had the odd problem with the usual things - tap microswitches, fridge heating elements etc. but the body seems as sound as it did when bought 2006. Keep looking round, but nothing I can see is sufficiently better to justify the cost of changing.
Also there is the 'devil you know' factor, particularly if you have fitted the mover and other bits yourself - you know exactly where any shortcuts have been taken !
You can always play the game ' If this was stolen or written off, what would I get to replace it ?' and if the answer is not glaringly obvious, stick with the one you know. This advice applies too none- caravanning matters too !