If you just want average 5-10 year lifetime, just pick up some regular Panasonic Blu-ray discs and you should be fine. Even with my cheapest burned media (TDK CD/DVD is almost all of it, I was a big fan), they all read perfectly today 10+ years later, except for several Maxell CDs that I didn't purchase myself which rotted. I hate that disc rot and really never trusted any Maxell discs after that! So in conclusion, if you store your (Panasonic) Blu-rays correctly and take care of them you should be fine for 5-10 years.
The following is talking about really keeping that archive alive and well and not overly thinking about price.
Now, if you use Verbatim/M-Disc's 100GB discs at $27 CAN or less if you buy more at once, you should get a few decades at the very least before having to transfer them to new media. They say it will last hundreds of years but I like being more conservative about it. I just purchased one of them myself to try out and they have a 10 year warranty on the package. So take that as the bare minimum lifetime but they should last a lot longer then that.
They are more affordable (per GB) then Panasonic's Archival Premium 50GB discs which are around $32 CAN each on eBay. I didn't purchase any (yet?) because it didn't make financial sense for the cost per GB and for my uses. I don't know which one would be considered the best for long term storage and have not seen any reviews of these discs.
I would say Panasonic made (I use That's 30-disc 50GB which is soon to be extinct thanks to TY shutting down) Blu-ray discs (25GB or 50GB) will last longer then any standard DVD will. Once you get into archival quality DVD's vs archival quality Blu-ray, that is another story and pricing situation, which will depend on where you live in the world.
For DVDs I use Falcon Platinum Archival discs. Cheaper then Gold but with all the benefits. Plus they are affordable enough to use as duplication discs, so my customers get nothing but the best without getting into serious costs.
Does that help?