You can order new sequencing reactions from stored samples within 4 weeks no matter if you have sent the samples in tubes or plates.
If you have sent the samples in tube format, just use the same order page and type in the initials of the respective sample. The system prepopulates all stored samples with these initials.
If you want to re-order reactions from a few samples originally sent in plates, you find the option "Re-Order from stored plates". Select the stored plate and specify the new reactions for the respective samples.
Under "My samples & primers" you can check the expiration date of your samples and primers.