Is a spare 35S a good idea or redundant?

[Gerald H]

Concerning battery life, today

2017-03-19

I put in fresh batteries in a 35s, the exhausted batteries having been inserted in

2015-05-??.

The calculator has been well-used in the 22 months the batteries lasted.

Concerning speed, the 42S takes about double the time to run programmes compared with the 35s.

I have myself written more programmes than fit into the 42S whereas the 35s memory is practically empty (or infinite, as you prefer).

Keyboard on 35s definitely dodgy, on some still performing well after 7 years use.