I have had this problem before, but just now i have closed X-Plane after lengthy 7,5 hour long session and ... i'm happy to report SMP did not eat my frames permanently!
Flew Europe from south to far north (LFKC-EPWR-EFRO) with the IXEG and SMP 3.3.2+RWC+FSGRW+MaxxFX (+XSquawkBox, X-Camera etc.). This included ~2 hr stop at EPWR with FSGRW constantly updating weather in the background (again, without shutting down X-Plane!). It might be worth adding skies are mostly clear over Europe today, no CB - but still SMP generated a lot of occasional cloud formations during that period.
Apart from some RWC issues (clouds sometimes popping right in front of my face at cruise) and IXEG VNAV/MCP bugs (i hope next hotfix is around the corner) i'm pretty happy with stability. I've alt+tabbed in and out of X-Plane around 200 times (the infamous Windows 10 update uninstalled), 20+ applications running in the background and X-Plane loaded/unloaded gigabytes of add-on scenery (including hogs like HD Mesh, Warsaw City+airport and Helsinki VFR with extended scenery on).
FYI, my SMP settings: