How long do batteries typically last for wireless door sensors?

[strangways@xxxxxxxxx]

Hi=20
Im looking for a self monitored system. I was anticipating wiring the senso=
rs up myself, which wouldn't have been too much of a bother, but it looks l=
ike most systems are wireless these days, which means easier install, but y=
ou have to replace the batteries. My system will require 3 door sensors. No=
 motion sensors.  How long do the batteries typically last in these wireles=
s sensors? If I can replace them spring and fall that would be fine, but if=
 its more frequently, then Id rather go wired.
Please suggest hard wired self-monitored systems. THanks