glo bugs are taken just about all year in taupo fishery although you may need to change colour and size periodically - these are rainbows we are talking about here.
Had stunning success on a gold beaded pheasant tail bomb last year in one session - in fact fish ignored the small glo bug completely but must admit not much luck on that bomb last session or two.
Browns may be a whole different ball game - much more fussy and if refused your offering first couple of times may require a different style as you say.
Rainbows and browns do strike out of plain annoyance sometimes regardless of whether the fly offerred replicates what they are actually feeding on - however if spooked of course browns esp will seldom take for quite a while but does depend on the fish. No hard or fast rule i reckon.
As to your question i have observed rainbows refusing flies for a period then pool rested for only 10 minutes or so and bang took first cast on same fly when fishing resumed.