Full-stops should be plentiful. To say this is to say that sentences should be short; and that is one of the first requisites in making your meaning readily understandable.
Always choose the full-stop rather than some slighter stop when what follows has no real connexion with what goes before. The following is the final sentence of a Press announcement of the beginning of a new term at a public school:
There are about 630 boys in the school, and the term will end on April 1.
It can hardly be supposed that the fixing of breaking-up day depended in any way on the number of boys in the school. There should have been a full-stop after school, and "the term will end on April 1" should have been a separate sentence.