Pinewood, I think you will find wild disagreement in responses here.
Okay, so my two pennorth is, I'm aiming for near-normal blood sugars, so I'm not a happy bunny spiking over 7.0. In fact I'm not happy with spikes at all. I try to avoid them altogether by getting the timing of Novorapid right, and when I manage that, I am a happy bunny. (BTW, what helped with that was a good Libre sensor.)
Because my A1c goes up if I even breathe a spike, more than my average BG would predict.
Sometimes, of course, it's not like that, but more like King Canute and the tide. When that happens there's no point getting het up about it, only in working to get down again.
I think up to 8 is not too serious, tho of course it's better to minimise the spikes.