My first jailbroken device began with a 2nd gen iPod touch.
At first I was afraid to jailbreak it since people told I would lose my warranty on it, but upon some further investigation,
I came to the conclusion, if something went wrong, I would just do a full restore.
I had that one for about a year and a half before I sold it to a friend of mine as birthday gift for his GF.
The night before I was going to hand it over to him, I put a fresh install on it, and when I was done and unplugged it from my PC,
I dropped it of the table, and the whole screen broke.... He still bought it, I did give him a nice discount on it though.
Then i had the iPhone 3g, which was jailbroken the first hour I got it, installed all the same tweaks I had on my iTouch, and some new ones ofcourse. I had this one for about 2-2.5 years till the point it got so slow, even when there was no jailbreak on the device.
I then upgraded to a iPhone 4, because the 4S had just come out, so I would save myself quite some money getting the 4 instead of the 4s. Again this one was already jailbroken before I had even put the SIM card in it. Redownloaded my favourite tweaks I had installed, and went on to find me some good new ones.
During this time I got myself a nice and sweet GF, she too bought an iPhone 4 a few months later after I got mine, this also had to be jailbroken ofcourse, because she highly addicted to a game she played one her samsung galaxy s2, and found out that I could hack the game with certain tweaks. After awhile she even got herself an iPad 2nd gen, which also had to be jailbroken....
I replaced my iPhone 4 about 3 months ago with the iPhone 5S, as it too was getting too slow, and I just can't stand slow things, even when it's people just walking in a shopping street.... And my mother was also in dire need of a phone, as he had dropped her phone in a bucket of paint.... And then tried to clean it with spiritus
The 5S got jailbroken as soon as there was an available jailbreak around.
I think this might be the last iPhone I will buy but not jailbreak, as I find the 6 too big, unless they come with a new model that is that same size as the 5/S.
I don't think that I will be able to go back to an iPhone that is not jailbroken, as I have so many tweaks, that make things just a tad
better, than the original interface or certain features are.