A quick thought! The D798 renewal reminder form may be sent out several weeks (6 or so) ahead of expiration but be aware if you renew the photo that early it means your next expiration date will be much earlier than the 10-year anniversary of the current licence expiration.
e.g. if your current licence expires 1st March and your renewal is processed 21st Jan, the new expiration date will be 21/01/2022 not 01/03/2022.
For maximum value apply for renewal close to expiration (i.e. within the last week).
If you look on the DVLA web site, you'll find various PO's which have a photo booth linked to DVLA specifically for renewing your Photo Driving Licence, wihtout the need to find a suitable Photo booth, and potentially mucking up the photo. I did this in May this year, and the new licence returned within 5 days. Made it so much easier, especially as I spend most of the week driving across the channel.
I THINK it depends on whether you have had a major change in your facial appearance thro' plastic surgery or accident. They know we all age but if basics do not change I see no reason for photo-change. Phone Swansea they are very helpful! Also if not done already, updating passport to digtal (todays or recent photo) is great help costing £70. Do not use a photobooth but professional photographer: checks and cuts to strict regs (about £6).
it is updated every ten years, obviously because we all age! the dvla will send out a letter a few months prior to the expiry date to ensure you have plenty of time to get your photos done. you can use a photobooth as they have special passport and driving license settings, or you can have it done at certain post offices who will do the photo and sending off for the princely sum of £25.00
you can get your own photos via a booth and sendoff your own application if you want, the photo card upgrade costs £20.00
It is the law that photocard driving licences MUST have the photo updated every 10 years. Driving with a photocard licence not having been renewed is punishable with a maximum fine of £1000.