Yeah I don't do these. I only do on-sites if I have a clear desire to work for the company. At the place I'm working at now, I did not do an onsite. At the place I was at previously, it was clear they were giving me an offer before I did the onsite, since the onsite was basically a 'get-to-know-you' thing. That's fine. On-sites serve a purpose of making sure you're not making a terrible decision. I actually made the decision this time to do two on-sites which is rare. This was because I had colleagues from previous positions at both locations and I honestly wanted to get a good sense.

However, one company was just really weird, so I learned that at the on-site. even though they wanted me... I said no. So in terms of preventing mistakes, on-sites are great. But, I'm not doing a 4 hour interview before any offer is made, or a clear indication of interest.