In the beaker now or beaker later equation you must also factor in the value on the GPT in unit maintenance that scientist will cost you to keep him alive until the tech you plan on beakering becomes available. If you don't factor this in you will wind up loosing a lot of gold carrying a GS a lot long than you should have. Unless there's a really high value tech in the not too distant future (Civil Service is a great example of this) I will use him to bulb whatever tech was next in my tech queue or a tech that will get me into the next era to open up more policies.
You can also just set your tech path, pop the GS and then shift+enter to end your turns. It does mean your tech path is set in stone until you reach a good place to exit, but you don't lose the gold. Considering you can do this with social policies, I consider the only reason they didn't with techs is because it isn't easy to support with the UI.