Your pilot takes the hit if your reserve is out and you get ramp checked by the FAA. There is no "grace period," if it is out it is out. Now do the math! If there is an accident of some sort an investigation will certainly follow and you, the pilot, the DZ and anyone else associated with it can be fined and/or have ratings suspended/revoked or both. An expired reserve has exponential implications particularly if a student is at issue. If the reserve had nothing to do with the accident, enforcement action by the FEDS may still be severe!!
Now, do you really want to put all of your friends at risk? You know, the pilot you like to fly with, the instructors you grew up with and respect, all because you are too lazy or tight to spend the time and effort to tend to your reserve? Come on, you are talking about $45 in most cases.
Your instuctor(s), never told you these things?