Well if 2 out of the 8 are gone you should still be able to toast at least two slices at a time on both sides.
As it takes approx 3 minutes to toast the bread to average toastiness, I would recommend getting out of bed approx 3 minutes early to make up for the toaster's reduced capacity.
However, have you thought of the downsides of toasting four slices at a time? if you have four slices toasted at exactly the same time - by the time you get to butter the fourth one, or even the third depending on knive strokage, the toast may not be actaully toasty and maybe a little hard.
So really it might make sense to only toast two at a time to ensure the bread is still hot enough to melt the butter as you spread it. A small price to pay for getting up three minutes earlier i would have thought. Plus you won't need a new toaster.
Unless of course you toast in a team when spreading butter on four slices of toast in a synchronised fashion will not be such a challenge.