Is there life on other planets and if so how frequent?
OK, so we know a couple of things about life in the universe. Note, however, that this is not really an answer and is also not very biological in nature.

So, we don't know how life began on the Earth. However, do know that:


The probability of life evolving on a planet in the universe is non-zero (since we exist) and, 
So far, we have not found evidence for life elsewhere in the universe.


So this leaves us with two main possibilities:


Life is rare in the universe.
Life is common in the universe but for some reason we do not detect it.


This latter possibility is basically a restatement of the Fermi Paradox which says 


  "The universe is very big and there should be lots of alien life out
  there. Where is everybody?"


In the case that life is common, we can speculate extensively on why we have not detected  it so far. For example:


We haven't been looking long enough (SETI has been running for only a few decades)
We haven't been looking hard enough (the budget of SETI etc. is not large)
We haven't been looking in the right way. We are currently looking mainly in the radio regime, maybe aliens broadcast in X (where X is part of the E/M spectrum or something else entirely, e.g. gravity waves, tachyons)
Life is common, but intelligent life is rare (this would be my guess) 
Life is common and intelligent, and doesn't want to answer (why? ask a xenopsychologist)


OK, so these are just some examples of "solutions" to the Fermi Paradox. There are many more which are much more exotic. My personal favourite of these is that we live in a simulated universe and the coders have not included additional alien life in the simulation. It would explain some strange "coincidences" about fundamental physical constants, but what simulation, no matter how good, would ever come up with cauliflower cheese for example?

However, until we actually detect life on another planet we will still be in the dark. The next generation of telescopes will be able to do this for nearby exoplanets if life is present on them and has affected the biosphere in a detectable way.

Edit - You mention "frequency models", but all we can currently say is that the probability of life on other planets is not zero - due to our existence - as I mentioned at the start

Some references:


A joint analysis of the Drake equation and the Fermi paradox, 2012, arXiv, Prantzos, N. 
The Fermi Paradox, Self-Replicating Probes, and the Interstellar Transportation Bandwidth, 2011, arXiv, Wiley, K.B.
Interstellar colonization - A new parameter for the Drake equation, 1980, Icarus, vol. 41, 193, Walters, C., Hoover, R. A., Kotra, R. K.