You can do that, but you can also use the camera clock to trigger your shots, see
http://chdk.setepontos.com/index.php/topic,3886.msg36423.htmlI'd have the camera shoot a whole lot more than once per day, though, since there's probably no reason not to.
A word of warning: we don't know for how long you can leave the camera powered on before it crashes or shuts down. There is an internal 10 ms ticker 31 or 32 bits wide, which will probably wrap around after 248 or 497 days after which either the camera or CHDK could do weird things such as shut down or freeze. So, it may be a good idea to periodically reboot the camera or at least to check that it still works. This ticker is just one thing that we know of, there could be other problems but other people are doing / have done slow timelapses like this before.
Anyway, there's currently no way to reboot the camera from a script (actually this has been done in mweerden's PTP stuff, but I believe the a530 is a vxworks camera like mine and his method doesn't easily port for them), meaning automatic rebooting requires some external hardware (example: set script autostart, mechanically fix the power button so that it's never released, use a cheap main timer to power off the camera external power supply for a little while each day). But for a month or few you shouldn't need that, especially if you're there to do it manually.
Also, shooting too many photos without rebooting will eventually cause a crash due to running out of RAM -- for my a570 this happens while entering the fifth (or sixth, can't remember right now) DCIM folder, setting a maximum of 8000 or 10000 frames when powering on with an empty card with photo numbering reset. Most cameras have more RAM than the a570 and may survive longer.
