You can claim a reward next day to get a stamp

You only receive a stamp for your first research each day. If you miss a day, the stamps *should* not reset (don't really know yet as we are only on the second day so far). But OP means if you are wanting to receive your 7th stamp reward as soon as possible, and you know you will not be able to play for a day, you can collect your reward for a previously completed research on your off day. You could at the extreme have three finished research waiting and have three off days in a row.