Jawa lifespan

Does any one know what the lifespan is on a jawa . i bought mine new . its got a season on it . it dosent smoke it runs just like it did when i got it. The lash has never moved . and it hasnt lost any compression . i run a leak down test after every race . ran same spark plug all season still looks new. Just curouis on how long should i run it before rebuilding it.i run a tillotson carb and it dosent contaminate the oil with alky like the speedway carb did.