Yes it’s okay to buy an exp, honest.
The exp is a fine kite for the occasional hour or two on a Sunday afternoon but if you want to take it seriously you’ll soon outgrow an EXP. In the same way a golfer carries a selection if clubs to cope with a variety of shots, a serious Rev flyer will want to have a selection of kites to cover different conditions.
The thing to remember with Rev’s is, if you have two kites, you don’t have two kites, you actually have two sails and two frames. Unlike a duel-line kite you can change a Rev frame in the field in minutes and end up with a totally different kite. It is very much a case of mix and match provided you stay within the same size, (and if we’re talking exp or B Series we’re talking 1.5). I don’t expect you to get your head around it now, but a very popular configuration is a vented sail (high wind) with light weight (low wind) spars. Sounds daft I know but trust me in the right conditions it’s sweet.
It is okay to swap frames between any of the 1.5’s, so you could, if you wanted, buy an exp now then at a later date follow it up with a vented B and later a 1.5sul and that would pretty much cover all the 1.5 bases but it would be a bit of a hotchpotch. Many people like to collect a matched set, my avatar currently shows my sul but I also have the std & vented to match. When I was choosing my first Rev the B series was not available and I had to buy three kites to cover all the bases and to be honest, if I lost the lot tomorrow and was putting in an insurance claim I would be looking to replace them like for like. However if I was having to start out from scratch again and it was my money I was spending I would go out and buy a matched pair of B’s - Job Done.
Another thing to consider is, the exp is an entry level kite the B series was originally aimed at the serious flier (though it is now very popular with newbies).
There is an old adage about dressing for work that might be appropriate here, “don’t dress for the job you have, dress for the job you want”, if you can afford the B go for it and if you are worried about justifying the cost, look at it this way, two B’b are way cheaper than a set of top end golf clubs and the wind is a lot cheaper than green fees.