Fixed rate ISA what to do should I fix for 1, 2 or 3 years?

Hi

Any advice welcome please, even if it's just what you would do.

I have 100k in fixed rate ISA, rate about to expire, going to transfer to another fixed rate (4.5) but wondering if to go for 1, 2 or 3 years, not intending to need any of it but presently taking the interest monthly to supplement income.

Thanks in advance