You could bed the front lug with enough clearance that the barrel itself would have no contact with the bedding. Tape the barrel well and let only the lug sink into the bedding compound. If your other barrel is a different shape you might have enough clearance anyhow to avoid a pressure point.

If you use a single lug it will probably be fine with good bedding but to take the chance of ruining a trip (along with the stock) due to a split would be too much risk for me.

To address the original question - I have split stocks more than once with 50 rounds or less. The wood will continue to shrink a little with age and recoil compression so it could happen much later but I have seen most problems occur at the beginning.