how long does the battery last

I assume you mean the hybrid battery. I have seen many 2003-2004 Civic Hybrid batteries fail already, so a 2000 Insight is probably more likely than not to have a battery nearing the end of its useful life. Try a local tech near you -- here's a list of possible folks to call: https://repairpal.com/honda-repair-in-seattle-washington They can point you in the right direction. The dealer, of course, is also able to help.