The autoblock feature intentionally makes these blocks last 1 day (or the length configured on the wiki). It also intentionally blocks only the last used IP address.

all IPs used by the user should be blocked for the same time

Blocking all IPs used by the user is not a good idea, given that most IPs are dynamic and so the user targeted by the block is likely no longer using IP addresses from say weeks ago

Blocking the IP(s) for the same length as the block on the user account would almost certainly cause more problems for other users, given dynamic IPs often change hands daily and autoblocking IPs for say a year would see other users use the dynamic IPs

Therefore, I'm going to decline this task because this isn't a bug with autoblock system

If you need to block specific IPs used by the user for longer than a day, you could ask a CheckUser to run a check on the user and block the IPs used by that user for a longer time (as I've done on English Wikipedia before)

Changing the autoblock system to make the length and number of autoblocks configurable would need further discussion in a feature request task (including the maximum length an autoblock could be), but without broader community support likely won't be implemented