Hi Peter, I was a carer for a gentleman who was on about the same as you for many years. And I recently went cold turkey after abusing opiates for a very brief period. I was feeling 95% after 7 days.
Here is a link I found extremely helpful. I found it too late but I already knew most of it except It took me a few days to realise I was in withdrawal. This link will help you and anyone else suffering unnecessary. I did cold turkey and there was no need for it.
Take this advice and you’ll be fine
https://www.reddit.com/duplicates/3hjbe7/the_definitive_withdrawal_survival_guide/