Whenever I sneeze so much that I can't sew, that's one clue.
When I can't find the table top to cut, is another.
But, when I have company, I have to move everything out of my dining room, because I don't have any other cutting space. For convenience, I just put the portable on the end of the table, and ironing pad near by, and thread bag on the chair, and notions all around, with little tv, heater and radio close by.....who could want more?