How long was a senators term of office in the late republic.

[drsrob]

A senator is not an elected office either, a person could follow the cursus honorum, and after appropriately filling a number of positions, pro formata enter into the senate as a matter of birthright, as long as you came from a patrician senatorial family and you had fulfilled the obligations of your station.

The senate was never a patrician institution, unless perhaps in the very beginning. You're confusing patrician status with nobility. Anyone who entered the senate became a member of the nobility (nobilis meaning "well known").

Sons followed fathers almost automatically. Unless someone like a censor had something against you, you practically couldn't be kept out of the senate if you had all the right family connections. Cicero was very proud of the fact that he was elevated to the senate su anno, in his own year, that is the first year he was eligible to be elevated. Cicero's career is a perfect model for how a person should progress up the cursus honorum. Octavian on the other hand demonstrates that many of these rules were fudged over if you had connections with people in power. He became consul at age 19.

A non patrician born person could get himself a post or a seat on the senate with as little as 100,000 sesterciis. This was not considered corrupt or a bribe, but a natural way of gaining funds and desirable recruits. Lots of positions were for sale.

The senatorship was generally not bought, though candidates for office had to use their own money to campaign for office AND to pay for the projects they organized.
One million serterces was during the empire the census minimum for a senator; in the late republic they had no census of their own.

Even then, many patricians who had the name and title never bothered. Being on the Senate was as much a problem as a benefit. Senators were more likely to be assessed, have their property seized, be censured, exiled or worse. Being in the senate was a risk, particularly during the republic. Senators were expected to pay out of pocket in times of need and many resented it. Many entitled to be senators never bothered.

Against all this disadvantages there were major advantages: the nobleman acquired respect and status and the money spent in some offices goold be replaced by money earned (or robbed) in others. In the late republic a senator had to spend a small fortune to become and be a consul, but he could earn a large fortune as a proconsul afterwards.

Still others changed their name and tribal affiliation to get out of the duty, and some became plebs because there was more political advantage to be had becoming a tribune of the plebs.

In the late republic one survival of the old struggle of the orders was that certain (religious) offices were reserved for patricians and certain political ones were barred for them. We know of one patrician who got himself adopted by a plebeian (and thereby becoming plebeian) to be able bo be elected plebeian tribune

That effectively ended with the civil wars and the assumption of the tribunician power by Augustus in 23 BCE.

What ended at this time was the possibility of acquiring the highest honours by following the traditional political career. And gradually the dangers of being a senator were no longer outweighted by the possible rewards.