How much would an 8-char case-sensitive one be?
An 8-char case-sensitive address would take me about 170 years to generate, so that won't be possible until I get better hardware. In contrast, an 8-char case-insensitive address would take about 5-10 days.
How much for 7-char case sensitive?
A 7-char case sensitive address would take around 3 years, so again, it's not currently feasible. A 7-char case-insensitive address would take about 7 hours.
Case-insensitive addresses are much easier because there are two possibilities for each character (capital or lowercase), instead of looking for one specific string. There's always the chance that a case-insensitive address could turn out lowercase, but running it enough times for that to be likely would take the same amount of time as searching for a case-sensitive one. There's also the possibility that the address being searched for could be the first one generated, but the odds of that are far, far worse than the lowest chances at SatoshiDice (speed is measured in thousands of keys per second, and it still takes hours to days for 5-char case sensitive addresses).