I have been on LTD for 3 years. How often should a case manager want you to check in if they have already approved you until age 65 and you are 56

You'll likely have a duty under your policy to report any significant changes in your health or employment/income to them (you can have a look at those terms in your specific policy for more detail). That said, for general updates, the case manager should reach-out to you. There's no specific rule about how frequently they might do that, although in same cases it can be unreasonably frequent, in which case a lawyer may have to get involved. If you've been put into "long-duration", then they will often only reach-out a few times per year.