I don’t know if there is anything peculiar to Victoria. In the ACT, where I am, a general meeting resolution without an explicit time limit would continue to direct and oblige the committee until it was rescinded or superseded or otherwise became obviously redundant.
That said, if the matter really is urgent, and two quotes are very similar, and you did diligently attempt to comply with the 3-quote general meeting decision, I think the committee could defend a decision in this instance to go ahead with only two quotes if it found itself being criticised. Make sure the reasoning and decision is clearly minuted!