I held a CPL for some time but was only flying privately. I revalidated my medical as Class 1 every time, but only when the Class 2 privileges expired, so every two years at my age instead of every year. Extra cost of a Class 1 revalidation is not that much, especially as IR holder where I need the audiogram anyway.
Your medical should say for how long it is valid for operations requiring only a Class 2 medical. I would wait until that point before revalidating, unless I was about to apply for something that requires Class 1.
To get the SEP rating back, all you need to do is pop up at an approved school, do training as required, get a course completion certificate, and fly a proficiency check with an examiner.
But I am really only repeating what Whopity already said.