Interesting question...
((First off.. hey everyone! Im back... again... It's been a while... But it's all good...))
I think this is a great question, because you're right - How can you deem a reading "accurate" when it comes down to personal interpretation...
Ive always said that Tarot "doesn't predict the future" - It gives you insight into the paths you can take to make something happen... So, instead of saying "when will I meet my boyfriend" you need to ask "what do I have to do in order to meet my boyfriend..."
If it was as simple as "When will I meet my boyfriend" and the reading said "next month" - And that actually came to pass - Then you could say it definitely was an accurate reading...
But, of course - This is not the case, and Tarot works more intricately than that... In my opinion, an accurate reading depends on the querants ability to be open to the experience - To be open to the lessons and the messages coming through - If they think and apply themselves to what's coming through, then any reading could be "accurate" when you think about it - But if they're putting walls up, or not willing to accept something... or not willing to be open, then nothing could be "accurate"...
Strange, I dunno if Im even making sense...
That being said... There have definitely been readings where Ive looked at the cards and thought "Nope... this isn't the answer to what they want..." - In that case, I tell them straight out - I'll tell them there are things here that don't relate to what they want to know, and I'll ask them if they want to me continue anyway, or try again with a reshuffle...
Ultimately, I think an accurate reading really depends on the querant, not the reader...