My house has evidence of previous termite damage....but it has been "clean" and documented for nearly 30 years by having an annual contract w/ a local company and they perform quarterly checks.
I've been in my house 4 years and haven't had any activity and when I bought my house I had the seller prepay for 5 years of the same service, through Varment Guard as well.
I think with today's monitoring practices and ability to correct issues it's much less of an issue than it was 20 years ago. I say if you like the house and it's a good deal, don't worry too much about it. Maybe do something similar to what I did, make the seller pay or give you credit for the monitoring service for so many years, for peace of mind.
I'm pretty sure the Varment Guard service is like $225/year and for as long as you have the service if you/they ever find more evidence or existing termites, they coverage your damage up to $1million, so plenty for my home.
My .02.