Risk free rate- t-bill or t-bond

CFA Level II
#1

So I did a bit of research of the “equity risk premium” which obviously can be estimated differently using different models, and I read the generic rule that:

t-bills should be used for one period

t-bonds should be used for multi-period

However, most methods prefer the long bond rate. Knowing that there are many models which have an equity risk premium involved (CAPM, Build up method, GGM, Ibbotsen-Chen etc), what are a list of consistent rules so that I know which rate to use for each model?

#2

For the exam, you needn’t worry about it; they’ll give you the risk-free rate.

For the real world . . . come back and ask on June 2.