Our patrols elect patrol leaders every six months. But we offer ILST only once a year, in winter. So the guys elected in summer get no training which seems like this is an unfair situation. I suppose we could get busy and offer ILST in summer. What do others do?

We also have 6 month terms and do ILST the week after elections. The only time we dont do ILST is if all the PLs have been through it one or more times.

Ideally ILST is offered any time you have newly elected leaders that haven't already had it.  If the times are inconvenient, you might consider trying to shift the dates of elections to make it more feasible.   

We're moving to yearly elections, so this should be simpler for me. Unfortunately, ILST remains an "optional" activities for my SM's. So, I slip a little into each PLC meeting and cracker-barrel. The obvious downside is that scouts receive scatter-shot instruction. The upside is that scouts who come on as leaders mid-year (usually to step in for an absent leader) get at least something. The personal upside for me is I'm forced to think about how to translate this to each troop activity, which has helped me be better at addressing leadership challenges on the fly.

IMHO, in your situation, @RainShine, if your leaders from last term are still engaged, encourage them to join the ILST. Maybe they can help lead it with insights from "The School of Hard Knocks." This is basically what I did with my daughter and her crew VP when we delivered ILSC for the council VOA. They had been in office for a while, never got the training formally, but had attended other academic leadership training programs, and they were pretty good natural instructors. Teaching the course filled in some gaps for them.

We offer it once a year to any 1st class scout who wants it. We add other lessons during the training, like how to sign off advancement and communicating skills. Our version of ILST is pre-required for being a patrol leader. 

Barry