I would definitely change them out. A cleaner/better spark sure wont hurt! I was thinking about changing mine out this upcoming weekend. Dont waitI'm coming up on 8k. The 8k service says to change the spark plugs. Do you think it would really be necessary at 8k? I'm running mostly freeway miles and the bikes running great. I'd just hate to change them out and then it runs not as good. Any thought?