A clutch type LSD will last a full race season before its recommended to be rebuilt. The OS Giken ones last the best and will do about 2 race seasons, not sure if they do them for Starlets though, might be worth a check but they are expensive. That's with circuit racing by the way so a lot harsher conditions than 1/4 mile drag racing. For little mileage I would always recommend a clutch type, however for a fit and forget diff that requires no special oils or running in then helical is best. Providing you can pay the little bit more for the gearbox oil every year, their worth having. There's no reason why a clutch LSD won't last 25 000 miles, possibly even more as long as the oil is changed at the recommended times.