LATE DSCNT; NON COMPLIANCE WITH ALT XING RESTR AND POOR ATC PLANNING.

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ENRTE TO SPS; WE WERE KEPT QUITE HIGH ONLY 15 MI FROM THE ARPT (ABOUT 16000 FT). AT ABOUT THIS TIME SPS APCH BEGAN GIVING US NUMEROUS VECTORS FOR OUR DSCNT. APPROX 6 MI FROM THE VOR; DSNDING FROM 8700 FT TO 8000 FT; WE WERE ASKED IF WE COULD CROSS THE VOR AT 2300 FT. WE REPLIED; 'AFFIRMATIVE.' AFTER RECEIVING NO CLRNC TO DSND FROM APCH; WE ASKED IF WE WERE CLRED TO 2300 FT. APCH THEN CLRED US TO CROSS THE VOR AT 2300 FT. IN THE DSCNT IT BECAME APPARENT THAT WE WOULD MISS THE XING RESTR BY 200- 300 FT. WE ADVISED ATC OF THIS PROB. SPS APCH THEN GAVE US A TURN AND HAD US CLB TO 3000 FT (FROM 2500 FT) AS HE ADVISED US OF TFC XING OVERHEAD AT 2800 FT. WE DID NOT SEE THIS TFC. AFTER THIS THE FLT PROCEEDED NORMALLY. IT SEEMS THAT ON VFR WKDAYS WITH THE ABUNDANCE OF MIL TFC; SHEPPARD ATC IS A BIT OUT OF CTL. I CAN'T RECALL RECEIVING SO MANY VECTORS IN SUCH A SHORT PERIOD -- FROM 20 DEGS TO 270 DEG TURNS. I ALSO REALIZE THAT WE DID NOT HELP ATC'S PLANNING BY FAILING TO MEET THE XING RESTR (OF WHICH WE ADVISED).