Re: Snaps or aplix in this situation?
I prefer aplix, BG aplix is pretty good. I think it might be tight but could last 18m (though i may be close). Drying the covers in the dryer occasionally can help tighten up the aplix hooks. I would recommend doing that every so often (not necessary a full cycle needed if you can remember to take them out).
Also if the aplix does start to give out, don't they have the same velcro tabs as the BG 4.0s? you could spend $8 on the refresher kits and replace the velcro if its needed.
that'd be my vote.