Old Collie + Arthritis + Wobenzym N + Metacam - Advice needed!

I have a 14 year old Wicklow Collie that has slowed down a lot and has
arthritis and back leg problems.

I have him on 10mls of glucosamine (Arthri Aid) a day and (thanks to a
previous poster on this group - and thanks a lot) Wobenzym N, one
tablet at night, human dosage and every 3 days he gets an Ashwaghanda
tablet.The Wobenzym N has done him a lot of good and three neighbours
seperately have said he is much better than a year ago.

Now, because the dog doesn't have long and because he started getting
old when he was 9 I am wondering about giving him Metacam say 5 days
on and 5 days off.I have read online that long term Metacam can be bad
stuff but because the dog has maybe a year or two I wonder what your
views are?

It is simply to give the dog a bit of comfort in his old age.Before
Wobenzym N I gave the dog Metacam 3 times over a few days to relieve
pain he was in and it had a good effect.

I want to know if I should use it on a more regular basis.

ps, the dog's appetite is very good, he is slightly overweight but has
no immediate health issues.

Thanks!