CoreBOSBB

I need import a big spreasheet, with 25.000 itens, what solution is better, change cron frequency or change values of number lines import each time.

I means, without causes any problem for my system, of course ...

make sure the cron frequency is high enough to not get launched twice.
that is a lot of records so you may run into PHP memory limit issues, but give it a try, if it stops you will know how many records get created in the system and can cut your CSV from there and repeat