The way i look at it is to calculate the impedance path from, say digital bond pad, to the clean ground path and compare with the possible impedance path from digital ground to analog ground.
For the bondwire resistance, i always assume 0.2-0.3ohm/mm and its corresponding inductance to be ~1nH/mm. So, depends on what kind of package you are using may result in different bondwire inductance and resistance. for example, if you have QFN package which provide you a ground plane, may have a downbond with inductance ~0.7nH. For BGA, which you may have more routing on the BGA substrate may give you more inductance. Thus, double bond or even triple bond may required for good isolation in this situation.