Depends on how long the chain has been in the engine period , the chains stretch over time , with or without the tensioner , if it sounds good for now , then run it the remainder of the season , during winter downtime , go ahead and do a refresh , even if its only the chain that gets done , since you have had it for a year and a half , and no major maintenance has been done during this time , winter would be a good time to do a workover , check the valves now , if they are out of spec , then they are getting ready to go , so over the winter when your not rushed to ride it , do the valves and timing chain , and check the piston , if the skirt is worn , then replace it , if you do all the work yourself minus the machine work on the head for the valves , you will get away with around or under $500 and you will be good for quite a while
I replaced my Piston , Timing Chain , and Intake Valves , including new gaskets for right around $500 , that was including machine work labor , just make sure that the shop has done or knows how to do motorcycle valve jobs , it is not the same as slapping a car head together , or have Ken here set you up with a fresh head , or have him rebuild yours **it will cost more , but you will be very happy in the long run** , if you go Stainless Intakes , you can realistically go 2 - 3 seasons or more with no maintenance with the exception of oil changes and air filter changes (air filter every ride should be cleaned) , my 450X has been on the same Stainless Intakes since late 2006 , and i have yet to need to adjust the valves , ........ keep Non Ethanol gas in it , and the carb will thank you , during the winter drain all the gas and either pour it in your car/truck , or save it for the lawn mower in the spring (these bikes do not like gas older than about 1-2 months max , they either won't start , or will be clogged up requiring a carb rebuild , and most likely a new Pilot Jet)
Other than that , now that it is relatively quiet , go ride and have fun
, then during winter , go thru it and be fresh and ready for spring ...