If all you want to do is lower your tolerance- tapering along with taking phenibut is one of the easiest routes. If what yo want is to take a break from kratom (permanent or not) you may want to look into using a couple of the washout tools. There's always the easier option of a gradually taper- only reduce grams on easy days like when you're off work. It may take awhile, but there's not a lot of hassle.
For taking kratom for years, I never experienced any significantly negative withdrawals. I just felt a bit "off" with some agitation. Although it wasn't a big issue for me, I know there's a substantial amount of people who say the withdrawals can really suck; and that taking breaks isn't easy. Whether withdrawals are painless or tough, always remember to prepare before you start.
I hope everyone can enjoy kratom as much as I have. Personally, the positives have completely outweighed any negatives it brings in my life. No back/knee pain, large motivation, and a compelling mood booster has been a real help. If this plant isn't for you, I wish you the best for a smooth painless washout. If anyone has questions or needs help with the process, feel free to contact me at anytime. Cheers!