Posted: 18/09/2013 at 11:48
Hello, Ashleigh, I spotted a message you posted up-thread and apologise for not replying sooner....anyway, first things first, welcome to the forum.
I've always found that seed purchased from specialist growers, such as 'Eagle Sweet Peas' produce superior blooms with longer stems. That aside, it is quite normal for the stems of all sweet peas to reduce in length as the season progresses.
Those in my picture above (posted 27/08/13) were grown by what is known as the cordon method. This is the system used by exhibitors and is preferred because it produces those long stems.