Is it me or is the canon eos spot exposure button a pain in *rse ?

YOu can target a grey card or some part of scene, press the spot exposure button and then recompose and take your picture. However, you have to options, either hold the button down while taking and composing the shot or pressing it once and then composing and taking within four secs.

Now for me, four seconds isnt enough to compose the shot, and keeping the button pressed while recomposing is a real problem as you only have one hand free to move the camera around on the tripod and fastening all the dials and knobs of it.

Do all cameras work this way, or is it just the canons that do it ? Is there a camera out there that lets you press the spot button and then take your time ?