Should I sell my working Galaxy S3 now and buy a new phone or use it till it dies?

[paresh996]

I have a Samsung Galaxy S3 which I bought two years ago. I've used it to the fullest and still like it. I've rooted it, flashed n number of ROMs and it's working Butter smooth now.
A thought just came to my mind of buying a new phone (just out of nowhere). Discussing with the people around, everyone told to go for it. I was firm that I'll not buy a new phone till I sell this one or it doesn't dies and becomes unusable.
Some say I shouldn't buy a phone just for happiness and change (just shouldn't waste money like that when the phone's perfectly fine). I should use it till it doesn't get damaged and only then buy a new phone.
But some said it'd be really better if I sold this phone and just put a little more amount in which I could buy the OnePlus One. I found OnePlus One fantastic and it's price is under my budget.

What would be a better decision? Sell the Galaxy S3 now and buy the OnePlus One putting some money or using the S3 for a year or maybe two till it doesn't get too old to run apps? Will I be in a loss if I sell it after a year or two and then buy a flagship phone?
And how much time do you think the OnePlus One will be a great phone to use? At least for another three years?

 

[Titillating]

The OnePlus One will be a great phone in the same way that the S3 will continue to be a great phone--by being a phone that works and does just about everything the average user will need.

That being said, both phones are a little dated. The S3 has long since been replaced, and this time next year we'll be up to the S7. The OnePlus One is being replaced by the upcoming OnePlus Two (such silly naming). If the OnePlus One is the phone you're set on getting, I'd say just continuing using your S3 for a while. Prices will end up dropping a bit more in a few months, I'd imagine.