I much prefer 15 heats. Especially the nominated heat idea. If a meeting's been decided prior it still gives something to look forward too.
Why look forward to something you've just seen 2 races earlier ( in 90+% of meetings)
Under the 13 heat system No 1's only met in heat 1 ( unless T/R or R/R ), therefore only meeting possibly twice a season ( 1 Home 1 Away ).
If my memory serves me correctly Poole visited Wolves 4 times last season meaning I watched Lindgren v Holder 12 times + ( possibly 3 times every other week in the GP's ). I was unable to travel to away meetings last year but if I did I would have seen the above 2 riders against each other 24 times plus a possible 33 times in GP's. This is a possible 57 times in 1 season ( not withstanding numerous times in Poland and Swedenn via the web ).
The old saying familiarity breeds contempt springs to mind, which I feel is a big reason for falling attendances.