Do you ever 'connect' to interviewers you spoke to on an onsite interview through Linkedin?

Just out of curiosity if you have Linkedin connection to people you only met or spoke through interviews?....

Some interviews last several weeks or months. Had great interview experiences. I have received several offers, and have to decline several of them as I only have one body.

So I have seen the interviewer only during the interview & I even have declined an offer from the company. Is it still ok to add them on Linkedin even after declining the offer?