It is not compulsory to frame my paintings, but if you like a more traditional look that is of course an option. Take this into consideration when choosing a size canvas as frames add a few inches to all dimensions.
I do not ship my paintings framed as they would be more expensive and more likely to get damaged.
To preserve the paintings I apply a coat of varnish. This means, should you need to dust the paintings, this can be done very delicately with a damp cloth without damaging the painting.