Impact on Recovery Time Using A Single Perpetual Base Backup and WAL Archives
I think the answer is &quot;it depends&quot;.
In my experience, the thing it depends upon mostly is the amount of data you are restoring, bearing in mind that the amount of data is the base backup plus all of the WALs since that base backup.
This means that:

if you have a large database (base backup) with few UPDATEs/INSERTs, then there will be very little WAL data to restore. In this case you can have a large period between base backups, with little impact on the restore time.
if you have a small database which is heavily UPDATEd/INSERTed then a large amount of your restore time will be spent replaying WALs. In this case having a large period between base backups, will lead to much increased restore times.