I don't know of any published spec for a 2610, but would be concerned if it is running over 70% consistently. If it is running high you first need to determine if it is truly load related, or is it misconfigured, or is there a process going berserk. show process cpu will let you see what process is using the cpu. In newer code you can do show process cpu sorted, which will order the list for you.
If IP Input is using most of the processor, CEF is configured on all interfaces, and the traffic throughput is indeed high, then maybe you need to step up to a new router. There is no processor upgrade available for a 2610.
If some other process is the problem, you will likely need to reload the router. The tty process has been known to occasionally act up on 2610s.
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