Data retention - lifetime prediction of modern calculators

[Leviset]

I have an almost vintage 1970s Citizen Quartz Chronograph still chugging along.
It's so old (Serial Number 91003821) and also says (4-098111K on back case) ) that when setting the date the year only goes up to 2009! You have to find a year below (<2009) which for 2018 is 2007 to match days/numbers of the week/month. It's lost its winder but the stem is still there to move and change the analogue hands.

I also have 2 1960s Bulova Accutrons in perfect running condition
Dennis