Looking for a used 2in1 thinkpad, not knowledgable about battery life in regards to specific cpus and models

Hi everyone! For the last couple of months i have been hunting for a 2in1 thinkpad, preferrably the x13 series but i don't know how each gen lasts on a full charge and i'm kind of paranoid. I currently own a lenovo laptop with a 13th gen i5 processor and it dies really quickly, which makes me hesitant to buy anything before g5. how much would you pay for an x13 2in1 gen 5? i'm in europe and they go for over €1k, no matter where i look. If you think getting an older thinkpad would be better, how's their battery life?