I'm torn on this issue. I completely understand why, as a diner, one would not want to be rushed or feel restricted to any kind of time limit. However, as a former server, I recall all too well the nightmare of customers who would occupy a table in my section for 4 hours or more, costing me tips, only to stiff me in the long run with a stingy tip. As a server I had no problem with people wanting to take their time, I just wished they understood that I paid my rent one tip at a time, and that by taking a table in my section for a long time I couldn't "turn the table" in order to get more tip by sales volume.
I once had a table with 4 adults. When they sat down they told me they were old friends who hadn't seen each other in a long time and wanted to visit, and warned me that they would be there for awhile. I smiled and told them they were welcome to stay as long as they like, and that I would stay out of the way and allow them to visit but always be nearby if they needed anything. I kept their drinks flowing, I kept their dishes cleared, I gave them plenty of space.....they stayed in my section for 6 hours. Their bill was over $150 and their tip was $5. On the way out they thanked me profusely for taking such good care of them, even stopped my manager to tell him how much they'd enjoyed their meal and my service. That's great, thanks, but it doesn't help me pay the rent. And the reality is that those people cost me about $100 in tips that night....between what they should've tipped for their meal and the amount of time they cost me in turning tables.
Servers live on tips, they still make only $2.13 an hour in almost every restaurant in the US. So if you want to sit in a restaurant for 6 hours and visit with friends, by all means, knock yourself out....but please remember that you are costing your server money, and if your service was really good or outstanding.....tip accordingly.
You know what...When I am at a restraunt longer than the meal, I always tip extra for that time there. It is just the moral thing to do for those who aren't getting tips on that table. Actually, I wouldn't stay if they are busy enough to have more customers at the table. The times I have stayed were when they weren't busy anyway, and then I still leave extra tip. It is just the right thing to do.