On the extremely rare occasion that I have an ender roll (maybe 5 machine wrapped enders lifetime), I do save them for last, but that is as long as I have ever waited.
Ender rolls would indeed likely sell for a premium on eBay, but if they are weighed and you're pretty sure the ender is the only silver in the roll, you are being borderline fraudulent IMO. Just like all those "unsearched" rolls of wheaties on eBay with a VDB, Indian head, 1916 Merc dime, etc showing. Technically you could word your description to be truthful, but its still a little deceptive. To me, "weighed" would be considered "searched"...even though it won't be 100% accurate every single time. I couldn't do it, but thats just me.
When it comes to weighing rolls of halves, a scale really doesn't help much...especially with the 40%ers. I have played around with a scale quite a bit and it wasn't helpful at all. For example, I have had an unopened roll that weighed 225.4g that contained 2 40%ers. I have had rolls weighing as much as 226.5 that contained no silver. I've seen hundreds of rolls that weighed 226g+ that contained no silver. I've had dozens of rolls that weighed less than 226g contain 1 40%er. With that said, every roll that has weighed 227.0g+ has contained either a 90%er or foreign coin, and never have I seen a 90% come from a roll weighing less than 227g...but I find very few 90% from MWRs. Maybe 5 or 6 lifetime that were weighed beforehand.