Yes it is a big deal jeffrey if that is how you are calculating your odds because you cant just add them together. Take the chances of not making your draws on each street and multiply them to get your odds of completeing by the river, or in terms of going all in.

If this were yur theory, if there were 3 cards to come instead of 2 then you would have a 90% chance and if there were 4 cards or more to come then yu would be gauranteed of making your draw. Of course there is never 3, 4, or 5 cards to come after the flop in hold em, but i hope you see the theory.

Talk to demiparadigm he is the odds master from what i can tell.