I have been using a Pi model B 512MB version 1.2 for several years. In total this server has been up for more than 5 years on different hardware. I started on a version 1 256MB. then to a 256MB that was back-powered through a hub. Then to a different 512MB back-powered through a hub. The Last version was a 512MB in a RadioShack project enclosure than had the power supply inside and hardwired.
Today I just moved it to a Pi2B. I have three of these early model Pi2's around they are the ARMV7 cores. So today one became an upgrade!
I backed up the Wheezy based Raspbian to my main system. Then copied it to a Sandisk ultra 8GB MicroSD. I have been regularly updating wheezy on the server So I was pretty sure the 2B would be able to work. Then used Win32DiskImager to burn the image onto the MicroSD. Next was getting into the router to change the MAC Address so the new board would have the old static IP. Use a 5.1V 700ma power adapter to power the board.
For once it just decided to work without a bunch of trouble. It is up and now I realize I should have done this a couple of years ago. Remote Administration is a whole lot faster. Page loads are faster but the WPFastCache has been doing a good job for me on loads. I did have to refresh the Cache as My brother was seeing some pages dropping out then reappearing. Refreshing seems to have cured that!
Total time to carry out upgrade; about 25 minutes. Most of it backing up and burning SD cards.
So if you have a 2B lying around doing nothing and a server running on an older Raspi, it might be time to just move it up a notch!
2015 Raspberry Pi model 2B (ARM V7 4 cores)
8GB Sandisk Ultra MicroSD card
Raspbian Wheezy LAMP with Wordpress
500MB (yes 500MB) USB stick as swap file. (not really needed any longer on a 1GB memory)
5.1V .7A USB power adapter