The newest is 8.3.5.231128, I think. The difference with 183522 is minimal. no use upgrading.
Elaboration on the previous posts:
DEM works on IGO8, it shows nice landscape views in 3D but eats lots of power
If speedcams are not needed, delete the speedcam content completely!
In short : delete every superflouos file, they have no use - or are not used at all - but eat resources while the s30 is low on resources and power. Keep at least one map (basemap is not needed either for a working program), one voice, one language and one scheme.
@ holyhead : fsp files for Primo only, well seen
Only I believe .ftr do work on IGO8.3.5 as well (never tried) as 8.3.5 is truck capable.
Edit
As I come to think of it, when the device is meant for a older person - who drives less? - it could be worthwhile to not upgrade but to downgrade to a simpler stable IGO 8.3.2 version. Those versions will be (should be) less greedy as they don't offer features like truck routing and driver alerts and ... Those features, though not used, use resources as well.