There a couple factors that determine the time it takes such as size and the conditions. In most cases, a concrete lot will need to be pressure washed to clean off mold/mildew. In that case, the lot would have to be washed then striped on separate days. However, all this can be done after hours or in stages that will not affect the business.
Lots can be opened up within about 30 min. after striping, 24 hours after asphalt work, 7 days after concrete and 24-48 hours after sealcoating.
There are many reasons a parking lot cracks. The base will move with temperature and moisture changes which cause the pavement to move. Concrete will crack if there are not enough control joints. Asphalt will crack over time as it dries out which is a normal occurrence from aging.