A PS just means that you will be seated within a reasonable amount of time of your PS time. You are guaranteed to be seated before someone with a later PS time or a walk-up.
When it comes to PS, I believe in better safe than sorry. We always make them, even if it's a supposedly slow time of year. I don't find it to be a big deal to be "locked" into an eating schedule because WDW is so easy to navigate.
I'm not 100% sure, but I think the week you are going could go either way in terms of crowds. If you are planning on celebrating Valentine's Day with a sit-down meal, I would definitely make a PS.
You definitely need a PS for the Princess Breakfast at Akershus in Norway. You cannot enter WS without giving your name/number to a CM with a checklist.
If you truly truly don't want to be locked into something the rest of the vacation, how about trying to make PS's when you are down there? You can call for free from your room in the morning to inquire as to what times are left for that evening. If there are only two of you dining, I would imagine that most of the restaurants would accommodate you easily without a PS. The only other one you may have a problem with and should probably book early is O'hana for dinner.
The number for PS is 407-wdw-dine. Don't forget to write your confirmation numbers down and take them with you.
Have a great trip!