Given the background description of some cooking related query, summarize the question into a title

[EX Q]: I'm a regular consumer of tea (since about 2 years ago), usually from commercial tea bags.They advise to infuse tea for 3 to 5 minutes, but there is some times that I have left it longer by accident.So I have been wondering what are the consequences -if any- of infusing tea bag longer than recommended by sellers (sometimes up to 10 minutes). My question is general, but I'm especially interested in black tea.
[EX A]: What are the consequences of infusing a tea bag longer than recommended?

[EX Q]: I've seen many recipes that use sour yogurt as a main ingredient, but I've been unable to find sour yogurt where I live, and I wonder if it's ok to use sour cream instead of sour yogurt.I know they're pretty much the same thing, but I'm not sure if it's going to change the composition/texture of the food by making this substitution. If it's not recommendable, what would be a good substitution? For example would it be better to use plain yogurt? Like the one sold at Walmart even though is a bit sweet. Thanks
[EX A]: Is it ok to use sour cream as substitute of sour yogurt?

[EX Q]: I live in Belgium and I can't find where to buy SOUR cream, which is amazing with quesadillas.Is there a way to make it myself?http://foodies.blogs.starnewsonline.com/files/2010/05/cosmic_quesadilla.jpg
[EX A]:
How to make the sour cream that some restaurants serve with quesadillas?