Simple Question about best h2 method

Hey all

I am seeking advice on the best method of using h2 titles,

An example...

H1 = Can Gerbils Eat Nuts
Text Here... Blah Blah Blah

I have many H2's on the page and I am unsure if shorter is better, or should I also target more keywords and google search phases but google may know already without?

Should I use H2's like

Introducing Sunflower seeds to gerbils
or
introducing sunflower seeds...

I will also have many more h2's on the page such as
Sunflower Seeds Nutrition for gerbils
or
Sunflower Seeds Nutrition


So in otherwise should I use what i think people will also search for in google in h2's or should I keep them short and sweet?..

Thanks in advance

Also interested in this!