If you're working a project on a full-time basis, the client will expect to be able to call you up and get you on the line at pretty much any time (and yes, often outside of normal work hours, in my experience). If you're on a "part-time" basis, you don't have this pressure because the expectations are set differently.
> the client will expect to be able to call you up and get you on the line at pretty much any time
I get your point but maybe it's the opposite in some cases? People want to have someone they can get at a moment's notice and when they find that person they are more likely to a) Use them next time (where price is less of a factor) and b) recommend them to others.
I say this as someone who has done quite well at consulting (and I do mean that) and that has no problem taking a call even on Saturday night. Now of course the devil is in the details and the particular client (goes w/o saying) but the counterpoint is that is how you build customer relationships and build a business. Fear of 'door number two' is what gets people to pay more the comfort of knowing someone is there for them.
I agree with you, and that's how I personally choose to work. There's a lot of folks who would prefer a different lifestyle if they could manage it though.
Ultimately, the number one thing that gets repeat business is results. Because of that, I can totally imagine people who offer a smaller time commitment still being successful. Regardless, I definitely wouldn't recommend going the 'part-time' route to anyone that isn't already established enough to get away with it.
If you're working a project on a full-time basis, the client will expect to be able to call you up and get you on the line at pretty much any time (and yes, often outside of normal work hours, in my experience). If you're on a "part-time" basis, you don't have this pressure because the expectations are set differently.