While away from home and not driving the car for around two weeks, I always charge the Tesla in storage mode. Storage mode should extend your battery life as it maintains the charge at about 50% of capacity. What can be a bit alarming is that when you leave on your trip, you have a certain amount of charge and upon returning from your trip you may have significantly less charge.
The loss of charge in the car is due to the batteries inherent self-discharge rates. For Lithium ion batteries, the rate should be 2-3% per month, but my non-scientific observation is that the self-discharge rate on my Roadster is higher than that when starting from a fuller charge. I try to run down the battery to about 50% charge before the start of a vacation.
The advantage of storage mode is that it extends the life of the battery significantly. I have on occasion tried to use the storage mode on a regular basis as I do not often need the full range capacity of the Roadster. Driving the car in storage mode is a bit problematic because the car repeatedly and unnecessarily warns you about the storage mode.