The Prodisc F01 blank media could be quite good. Take a look through some of the scans in this thread in our Blank Media forum: http://club.myce.com/f76/prodisc-dvd-r-77177/index2.html Look for low PI Failures in the scans. Under 1000 is very good.
It could also vary in quality sometimes, like many types of blank dvds.
I never used it myself.
If your 5yr old burns are still playing well, I'd say you have a reasonable chance of these new burns doing as well.
We don't normally advise buying Memorex, because they can be virtually anything...they have a history of changing suppliers without warning. Your particular disks are extremely surprising. I haven't seen MCC-004 disks under the Memorex brand in years. MCC-004 is manufactured by Mitsubishi Chemical, and is normally seen as Verbatim brand disks. They are the main type of disks that we recommend. (along with Taiyo Yuden). Do you happen to still have the external wrapper on the cakebox? If so, check the country of origin. I suspect it will be Taiwan, but it might be India or UAE.
In any case, the MCC-004 disks should be very good. But in the future, I'd advise buying Verbatim brand.
Media is a fairly important part of the equation, so buying the best available is always a smart choice.