This is disingenuous. Prorogation is usually done for short periods, at times that make sense, such as elections or the expected end of work. They are seldom controversial. Harper's current prorogation - shutting down parliament for a prolonged period to halt a parliamentary committee's investigation into government malfeasance - is most definitely not routine.
We should have learned during last year's federal crisis that we can't allow Harper's spin team to turn lies into conventional wisdom. Last year, Harper managed to convince Canadians that the coalition was undemocratic. This year, he's revving up the spin to convince Canadians that this prorogation is perfectly normal, business as usual.
I haven't been able to find information about the exact context of past prorogations. If anyone has that info, please let me know.
Update: The PMO released another talking point on prorogation, claiming that Chretien did it more than Harper, and specifically citing his 2003 prorogation as a way to avoid release of the Adscam report. This has been widely pasted into comments sections of newspaper articles and blogs, including this one. They neglect to mention that the prorogation occurred when Paul Martin took over as leader of the party. Since prorogations are supposed to occur when it is time to reset a legislative session, this seems in keeping with tradition, as a new PM would surely be resetting the agenda.
Update: Only in Canada: Harper's prorogation is a Canadian thing