Here is a quote found from the Internet, however I don't quite fully understand its reasons and implications yet. Q A Deep in the Money LEAP doesn't have much Time Decay, but it is something to be careful of when the stock gets closer to expiration. One should never buy a DITM that is close to expiration without serious consideration. UQ
If trading below intrinsic, often better to exercise option and simultaneously buy/sell underlying (,depending if put or call). It depends on how much below parity and commishion structure.