I think the valve clearance check is just a recommendation from Suzuki, if the bike has been serviced regularly and not seen much track use then I wouldn't worry about them, unless it is getting hard to start or noisey etc that would be only time I would spend all that time/money getting them checked. I had a 2001 r1 with 30k on it, it sounded noisey so I payed £200 to get them checked and they were all fine! And the bike sounded exactly the same after, so I wouldn't worry.
