I would say yes to putting him on something like dasuquin as a maintenence , it won't 'prevent' things, if they happen they happen, but it won't hurt to supplement him.
Swimming is good for muscle tone, and keep him lean..
Danger Danger vom Kleinen Hain aka Masi
"Angel" Jakoda's Bewitchen Sami CD OA OAJ OAC NGC OJC RS-O GS-N JS-O TT HIC CGC
"Angel" Steinwald's Four x Four CGC HIC TT
Harmonyhill's Hy Jynx NA NAJ NAC NJC RS-N JS-N HIC
Jakoda's Jagged Edge