Depends to be honest. I've just lost one. Was fine the night before and found him the following morning collasped,shaking and cold. He passed about 20 mins later
no signs before! I lost one in march 2015 and she was in a hunched over position, stopped eating apart from cucumber, scrambled egg and baby food. Wouldn't drink very much at all and ended up passing after a week. Have no clue what was wrong, but think one was old age and the other possibly had wet tail or cancer x