The InTice 10 Perimeter Bait has a shelf life of 1-year if opened, and 3-years if not opened.
Yes, as long at the area under your mobile home stays dry you can use the InTice 10 Perimeter Bait, and it should provide up to a 90 day residual.
Intice 10 will not work for springtails due to their feeding habits. We would recommend trying a dust such as Delta Dust in and around all of the cracks and crevices where you are seeing activity. Delta dust is a good choice because it works even if it gets damp and it lasts up to 6 months. We would further recommend that you treat the exterior of your home with Talstar P. Pull back any mulch, straw or plant bedding at least 6 inches from your home. Make sure your gutters are in good condition and are not causing water to pool against the structure.