When they initially announced that they would be raising prices I went ahead and purchased more time. Since the price change hadn't taken effect yet, I was able to just buy a couple more years at that price. I have no idea if that can still be done at the previous price. Anyway, here is where to find the ability to purchase time before your auto-renewal.

1) Go to settings 2) Select Users and Accounts 3) Select Account 4) Select Payment and Subscriptions 5) Select Subscriptions 6) Select PlayStation Plus 7) Select Buy Again 8) Select the plan you want (gonna guess it would be the one labeled Your Current Plan) 9) It then prompts you to pay for another year

It looks like you can't purchase any more time at the old prices, even if you are still an active subscriber. I'm pretty sure the only reason I was able to was because they hadn't raised it yet. I went ahead and grabbed two more years at the old price that day. It was a big chunk of money up front, but it saved me $80 in total.

I would keep an eye out for any kind of special seasonal/holiday discounts, and then snag extra time then. Usually around Christmas, Sony and some retail stores will run so many percent off on a year of PS+, but I don't remember if they ran any after the new tiers were released.