Any photo will automatically delete from MDE 45 days after they are taken. Once you download the first photo on MyDisneyPhotoPass.com or the My Disney Experience Mobile App—or otherwise redeem your Memory Maker purchase—you then have 30 days to capture more photos.
As such, if your trip starts on January 1, you would need to activate your 30 Day Memory Maker Window by February 14th otherwise you would risk losing photos from the beginning of your trip. If you activated your 30 Day Memory Maker Window on February 14th by downloading your January trip photos, you could continue adding photos to MDE and download them with the same Memory Maker pass until March 16th. (And double check those dates for accuracy)
As such, yes, it is possible if you wait to download your photos as long as possible and so long as your trips are beginning or end of January and beginning or middle of March (and not beginning of January and end of March).
In either case, you would not be able to see all of your photos (from both trips) on MDE at the same time. You would need to download the January trip photos, they would automatically delete after 45 days, then you would download the March photos as soon after your trip as possible (if not downloading them the same day(s) they are taken).