Ref - L-OS71641700 -
For 21VZ and other T-type head (Turbo head) 21 class racing engines. All seasons
Yes this is an all weather plug, be it summer or spring or autumn - this could suit your engine!
Glow plugs are considered to be consumables - But by using a low voltage to start ( under 1.5 volts) and not burning the plug dry, you prolong the life of your glow plug. It is also worth washing out a new engine after running in to prevent small particles shorting the plug and destroying it. Blowing plugs on new engines is less common now a days, but is still something that can happen.