In order to maintain unconditional stability, The Rollet factor(K) value should be greater than 1.
Does anyone know how far the value can go above 1 so that the stability condition is still satisfied?
I came across a particular LNA in Minicircuits which has a K value of nearly 12 at some frequencies whereas some others maintain values within 1 and 1.5.

 

For unconditional stability k>1 and B must be +ve. When k>1 it will always be stable, so don't worry if you see numbers like k=12 etc. For a better idea of absolute stability use Mu and Mu' , these are geometrically derived parameters which indicate how stable you circuit is, the higher=more stable. One downside for this extra stability can be a lack of gain, as the designer may have used resistors to control any potential instabilities.