Even on-chain timelocking is risky because one mistake and your coins will be locked for way longer than you intended. But I always found timelocking in general a very poor practice. You don't know how the future will change. Maybe you or your loved one will get cancer and you will need all the money you can get, but because you bought into the HODL STRONG HANDS NEVER SELL meme you will lock yourself out of the very much needed funds. If you have problem with self control then you should solve them instead of making some gimmicks that deal with the symptoms and not the cause.