boil time, am i missing something?

I'm going to be making an Irish Red Ale tomorrow. The recipe I'm using calls for a hops bittering addition and no flavor or aroma additions. It occurred to me that instead of adding 1.25oz of EKG with 60 minutes of boil to go I could add 2.00 oz instead at 21 minutes to go. This will give me the equivalent IBU's and would add some hop flavors as well. If I decide to add the hops at 21 minutes remaining in the boil is there any reason I have to boil much longer than those 21 minutes. I would wait for the hot break (15 mins or so) and then start my timer. Best I can tell there's nothing wrong with this approach, but I'm an uber novice, so I'd love to get the thoughts of you seasoned veterans.

Thanks!

The approach is fine.  I have done a couple 15 minute hop only additions with good success. 

The challenge is knowing how much isomerization will really occur and how smooth or course the bitter will be.  A smoother bitter is nice but can also leave the drinker thinking the beer is sweeter than it is or a little thin like.

The isomerization is more predictable at longer boil times so the calculated IBU level is more reliable.  I would go with your plan and see how it turns out.  I find following the software too close is rather confining.

Assuming you are using extract you can use this approach.   

Some of the reasons you would want to do a longer boil:

• Drive off DMS from very light malts
  Melanoidin formation (toasted flavors)
  Wort concentration (Kettle caramelization possibly)
  Protein formation
  Sterilization
  Isomerization of alpha acids

Some of these are process related and extract brewers won't need to worry about them as the malt extract process will take care of it.  Others are style dependent and can be adjusted by the recipe.    For a Red Ale you may be able to get away with adding some red malt for color and sweetness that could come from the longer boil. 

Give it a shot and see what you think.    Pick clean flavor hops so the short time will not produce a strong hop flavor.   

One final question, how long does it take you to cool down your wort post boil.    If you are at a high temperature for an extended period of time you will lose a lot of the flavor anyway.

Thank you for the replies. Let me clarify some things I didn't post originally. The Red Ale is an all grain recipe/process, with the base malt being Maris Otter. I used EKG hops. The rest of the recipe consists of Rye malt, Caramunich, and roasted barley (25% of grain bill). Here in Colorado our winters are chilly and our ground water is awesome for cooling the wort (I use a wort chiller). I don't think it takes more than 15 - 20 minutes to cool the wort this time of year. How long would you consider an "extended period of time"?

I'm definitely interested in this process change, but since I'm such a newbie I don't want to make a bad batch of beer either (my fingers are crossed, I've not made a bad beer yet).

Thanks!

Interesting post. If what you do works for you, then keep doing it.
I usually under hop or use shorter boiling times for my taste. I think that the shorter boils give a fresher, crispier taste.
The longer boils give that deep down bitter taste.
Just my opinion.

Understanding the hop is very important.  A hop like EKG does not have a lot of cohumulone which makes the bittering less harsh.  So, reducing EKG to 21 minutes just wastes hops.