Not very well . 9" is too large for an 8" system. At $48.70 for each 12" piece it would be a spendy riser... mine is 52" tall in an 8" system... so $243.50 for a 48" riser... not cost effective even if they combine shipping.
I build my risers any height I need, using fireclay/perlite, an 8" id sonotube and a 16 gallon grease barrel as an outer form... total cost might be $40.00 ..... "broaudio" on you tube will explain how to cast risers.
Short answer , A LONG TIME. My first one lasted 3 years , what failed was the 16 gal barrel got rusty at the bottom edge and tilted, which caused the riser to crack. If not for that happening that riser would still be in use today. One of the nice features of building a riser this way is the ability to uncob and lift it off of a core if (or when) you go in to modify your core unit.
Of course if you can afford it the "newest... best.." thing in RMH's is 1" thick ceramic fiber board or tubing being used for cores (other than the feed tube) and to build risers. The downside is the cost... I haven't spent the money on ceramic fiber boards yet myself, but the performance reports are so good that they will be used at my home sometime in the future.
Inside the riser they say 1500-1800 F or more in a batch box. Top of barrel at my rmh has been seen at 1100 F Normal barrel top is 800 F exhaust pipe where popping out of the mass is 130 F Top of stack same thing 130 F
Inside the riser of a batch box 1050º C (1920º F) is quite normal once at operating temperature. Theoretical maximum of an atmospheric-aspirated wood burning device is 1200º C which is the equivalent of 2190º F. I have one recorded figure of 1172º C (2140º F), very close to that maximum.
For my PvdB 6" batchbox I went with an IFB (Insulated Fire Brick) heat riser (2600° F. rating) sourced from a local Harbison Walker refractories outlet (many locations scattered around the US). Anyway, three seasons down and the heat riser is going strong, and is expected to last for a good many years yet to come. It took three cases of IFB for the heat riser construction, and the cost at that time was in the range of $120.