Working untimed and using the streaks method to develop skill in getting questions correct consistently is great. By shooting for streaks, you learn to do all the things necessary for getting questions correct consistently, such as reading carefully, answering the question asked, etc. This is a great outcome that helps to ensure that you achieve high accuracy on test day.
At the same time, it's also necessary to build speed and to learn to bail on a question on the test if you're bogging down.
So, there are a few things anyone experiencing timing issues after using the streaks method can do.
One is, once you're getting questions correct consistently, rather than jump directly to timed practice, work on shaving down your time per question. For instance, if you're getting questions correct in long streaks, but it takes you five minutes per question, look for ways to reduce the time per question incrementally.
In other words, first work on getting the time down to four minutes per question, then three minutes and thirty seconds, etc., all while maintaining high accuracy.
You may need to adjust how you're answering questions to reduce the time you spend on each question. In other words, you may need to develop additional skills. That doesn't mean that the streaks method didn't work. It worked for developing accuracy-supporting skills. It's just that now you need also to develop speed-supporting skills. Everyone needs to do both to score high on the GMAT.
The other thing you need to do is learn to bail on a question on test day. So, once you've learn to answer questions faster, you can do timed sets to develop this additional skill by seeking to complete each timed set at test pace and bailing on any question such that you can tell that you're not going to answer it in a reasonable amount of time.
In short, the streaks method helps with development of certain skills, and at the same time, you need to practice in additional ways to develop other skills that are key to scoring high on test day.
For more detail on how to use the streaks method to develop skills that support high accuracy, see the following post.
How to Ace the GMAT Using the Streaks MethodFor some examples of people who used the streaks method to get good results, see the following posts.
Used the streaks method to achieve a 90-point increase to 755Used the streaks method to achieve a 100-point score increase in a few weeksMastered RC using the streaks methodMastered CR using the streaks method