Boil times

[Mont Y. Märzen]

Go ahead and shorten to 60 minutes. The extra 30 minutes boil time has virtually zero value in any way.

I think that's a matter of personal preference. I've experimented with various boil times, and my beers are consistently better and score better in competitions when I boil vigorously for 90. 60 or less, and softer boils, has always been a lackluster result for me. I suppose it depends on your system and your desired level of extra 'umph' in your brew. And as a side note, I *never* use Pilsner, so that's not a factor.

 

[Mont Y. Märzen]

Theakston Old Peculier​

Iam looking at giving this recipe a go, but 90min boil time , can i do a 60 boil time .and just adjust hops to get same ibu
Do i gain any thing from a 90min boil

The BF Recipe calculator will help you adjust your additions either in amount or timing to hit the IBUs you want for different boil times.

I'd put the recipe into the calculator as-is, then drop the boil time to 60, adjust hops as needed to match the previous IBU target, but even more importantly, adjust your water requirements to match the lower boil-off loss. You don't want to thin the beer out, end up with extra wort that won't fit in the fermenter, hit a lower OG, and thus throw off your BU/GU ratio.