I would say, it is up to you. maintenance is easy on the Savage, but if you got your S40 from a good dealership you feel you can trust, you make the decision. Myself, I bought my 06 S40 from a very good dealership, and I took my S40 in for the scheduled 500 mile check, and yes they did check the valves, belt tension, oil/filter change, etc.. My next check was at 3000 miles and they did the same, and made a minor valve adjustment for me. I checked with them at 5000 miles and all they did was ask me if my milage dropped, started good, ran good, good performance, etc., and said there was no need for them to do a full check, only an oil change.
Like I said, I got my S40 from a good dealership who thinks good honest service is the way to keep their customers. I know they are all not like this.
My warrantee runs out in July, and that is when I will do everything myself unless something big comes up that I fel I can not handle.