With SLM 7.1 (as well as the current SLM release), asset availability service targets only provide time-based goals/tracking which allows you to monitor the amount of time the asset is available or unavailable over a given lifecycle. However, you can associate milestones and actions with these service targets that will trigger based on the number of "down" or unavailability counts within a lifecycle. I'm sure you could also come up with a creative customization that may meet your needs but I'm not aware of anything delivered as part of the solution.
I would suggest entering a request for enhancment (RFE) with BMC Support if you would like to see this type of asset goal in a future release.
Sorry I couldn't be of more help.
One other suggestion - use a ProactiveNet service target instead? I think I remember PNet making these types of counters available as KPIs for SLM. Don't know if that's an option for you...
I'll try to go for cstomization for this. Thanks again.