How long is the wait to get a penta after a quadra?

A while ago it took one freaking minute for a Katarina to get her penta chasing down an orianna all over the place.

Meanwhile I recall my friend trying to get penta after her quadra by doing the same, chasing down the 5th enemy and it was like less than 1 minute around 30-40 seconds and once she killed them, NO PENTA!

I'm so confused. Is this normal? What are the wait times for that penta to happen? I thought it was a problem. Not sure.