Speeding up REGex expression

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I am a complete newbie when it comes to REGex expression.
Previously I would have used 0000000 S##E## but that did not seem to work.
I am currently using ^(?:(0000000\s[Ss]\d\d[Ee]\d\d)) as an expression to limit the searches.
But the searches become soooo slooooow. I tried to be as specific as to what to look for, but that does not seem to help much
Is this simply just the nature of the beast?
I have even made QuiteRSS a priority program but still...