Co-Signing?

So I need a new car, and was looking into a lease. My credit is good but the thing is, I work part time as I’m also a student in university. So I applied for a car lease, and they come back and say I need a co-signer because of my income. Which my boyfriend and I predicted.

I’m kind of conflicted though because I asked my boyfriend if he could co-sign for me, and he said he would but I have to promise to make every payment. I obviously would, I never miss any payments of mine as they do reflect my credit and I wouldn’t do that to him. Is this a good idea? When I was telling my best friend, she was saying not to because what if we break up. We’ve been together for 3 years, and we’re engaged. The lease is a 3 year lease as well so I didn’t think it was too long but now I’m questioning it.

Would you help your SO out like this? Is doing this a bad idea?