Why am I on my 3rd Roku ? and do I have to renew my subscriptions ?

Fortunately or unfortunately, technology marches on and devices become obsolete when they can't keep up with the bloat features that Roku or app developers add.  If your subscriptions are through "Roku pay" then they're tied to your Roku account and as long as you link your new device to the same account as your old account, the subscriptions will immediately be available on the new device - you don't need to do anything.  If you've taken out subscriptions directly with a provider then you may have to sign in again the first time you launch the channel/app on your new device.