How long will an aquatic turtle last after buying it from the pet store?

aquarium is needed because they need to be in around a 75 gallon aquarium almost full to the to with water. they can get shipped without water they would be find they easily last over 20 years some last 40 years. but for their habitate they will need a 75 gallo naquariuma heater so the water stays at 80 degrees an good filter because there dirty a basking dock wit ha basking light ( uva/uvb rays) they need protein rich diet for the first si months then they switch to protein and vveggiesthen after 1 year they stick to mostly vveggies