its up to you, for my tenants that rent for long time I never update the agreement but if you want to raise rent then better draft a new one and have them pay the extra for deposit and etc

there are lots of tenancy agreement samples on the internet, just use one of them and edit the contents. I did all my TA myself and bring it to LHDN for stamping after its signed by my tenants. Only cost to me is to print it out and get transportation to LHDN. The cost of the stamping is borne by the tenant. I've always make a 2 years agreement with a clause that they need to stay min 12 months to safeguard their deposit and reduce the times I need to go to LHDN

Unless the monthly rental had changed its just continuing with what I have collected, if there are a raise in rental then I will collect the difference to make up the deposit