It rather depends on the path of the comet. Some comets (such as Encke's comet) return in as little as 20 years - others might not return to our solar system for centuries (Comet McNaught has an orbital period of over 92,000 years !) It's possible to see at least one comet per year if the weather conditions ar favourable.
TELESCOPE
because god sent them for us to see. hail almighty god.
Typically, several comets are spotted every year.
A comet that takes the same time to make its orbit of the Sun. We can predict with a good degree of accuracy as to when we can see it again. Halley's Comet is the most famous, coming about every 75 or 76 years. It is not totally precise as it can vary, so we can only say about every 75 or 76 years.
Comets spend the majority of their time in the far reaches of our solar system, where they are not easily visible from Earth. They only become visible when they enter the inner solar system and are illuminated by the Sun, hence their rare appearances. Additionally, many comets have long orbital periods, further contributing to their infrequent sightings.
There is no set number, because new comets are discovered all the time. Not all comets that are discovered will be visible with the naked eye.
they have long elliptical orbits
they tend to move past in routines orbiting our solar system or our galaxy in about 70 years
TELESCOPE
short period comets
See related link for a list of periodic and non periodic comets.
when your balls drop
Short period comets have a period of less than 200 years Long period comets have a period of more than 200 years.
Absolutely. You can see comets pretty much anywhere they pass between Venus and Mars, when they are opposite the sun from us. On the day side sunlight obliterates them from view. Hyukatake and Hale-Bopp were two prominent comets within the past twenty years. Beyond Jupiter they are much harder to see, both because there is much less outgassing and because of their relative size. Such comets are typically found only in fairly large telescopes.
long period comet
Comets have been around for the past four and a half billion years.
Because there aren't always comets!