Hello all!

I went to school in 2004-2009 and accrued about 10K in debt in the form of DL Sub, DL unsub, and Perkins.
My rates for these are low (under 3%).

I have yet to find ‘professional’ work or work in my field (biology). My loans are kind of stagnant. I currently work PT at a college. I then went back to school for a year mostly because I was unemployed and couldn’t find a part-time job (any job) and needed some sort of structure to me life (no regrets). Also, I wanted to update my skills. I took out a small amount of loans, a mix of DL Sub and Unsub. These are currently on a standard plan and I’m currently trying to figure out how to redirect all my loans.

So, the stats:
Disbursed 2006, currently under IBR (which I’m overpaying monthly right now, preparing to recertify)
-Unsub DL @ 2.4
-Sub DL @ 2.4
-Sub DL @ 2.4
Paid on and off (deferments, etc), but no missed payments. Probably at least 3 years of payments already.
Serviced by Mohela

Disbursed ~2006
-Perkins @5%, I pay $120 a quarter

Disbursed 2015
-Unsub DL @ 4%
-Sub DL @ 4%
Just started paying a few months ago, need to switch to IBR (still on standard)
Serviced by NN

So far, these are all undergraduate loans.
Right now, I am not a “New Borrower”

So my questions are:
Say I switch both plans to REPAYE (not sure how relevant this part is).
What happens if I pay off the first ‘batch’ of loans from 2006 in a few years?
Will my 20 year period still start in 2009?
Or would it start in 2016?

I would think it’s best to pay off the new loans first. They have a higher interest and I probably won’t actually end up using Forgiveness (but I still like the security of it as an option).
Bonus= maybe keeping my repayment period started in 2009
Drawback= could I technically be a “new borrower” if I paid off my 2006 loans. At the time of the new loan disbursement I was NOT new borrower, but could those loans become ‘New borrower loans’?

Question
Wait, are these loans even subject to the same repayment period cap?
If I leave 2006 loans on IBR and move 2014 loans to REPAYE, do they’re 25/20 years start at different times (2009 and 2015)?
What if I move them both to REPAYE? Same IDRP but still different loans with different repayment start dates?

(apologies for typos, this laptop is hypersensitive)

I don’t think it will make a huge difference for me on my own, but I’d like to get a really good handle on these factors before I start considering potential spousal income/loans, going back to school, etc.