Playpen once baby has started to climb things or stand up

My mummies, im currently using baby playpen as baby cot, like those joie ones that have 2 levels, up and down. However once baby is few months old or coming to a year old and already attempting to climb up things or stand while holding the playpen sides, do you bring down the mattress to the bottom level? And let them sleep at the bottom level also? Do you have difficulty carrying them out or in from that level ? Fyi my bb is coming to 2 months just want to know in advanced