It would allow him to heal 10% so it will keep him alive although afflictions will come from the diesiese, and a lot of them. If he has magic paths whitch you don't want to loose get ring of regeneration. If he is pretender without paths its better to let him die and be reborn:P
Although even with ring of regeneration your pretender will at some point get the "mute" affliction

so his magic paths will be halved, after that if you want to get his magic paths back you'd need Gift of health/Faerie court/The chalice to get rid of his afflictions.
Although if he gets feeble-minded affliction(reducing his magic paths to 0) Faerie court won't be able to help you, only The chalice and Gift of health.