My engine builder wants to put in solid roller lifters but I am hesitant due to the horror stories I have heard and the maintenance involved with them. How often should they be checked? I don't have the cam card in front of me now but we have stud girdles.
Its a 555 tall deck that made just under 700hp last fall.

I see no reason to go with a solid roller unless you want to spin the engine beyond 6000rpms.

I've ran solids the last 7 years. When I ordered my new hydraulic roller cams I told Bob M. that I just had my solid Isky Red Zones rebuilt and I would like to still utilize them. He had no problems with me running them on my HR cam and down the road if I would like to use HR lifters he said that I would have no problems. I spin my new engines to 5800RPM, but 6500RPM on previous cams. Maintenance is checking lash every spring. You should never have to adjust lash if set properly, if you gain or losing lash you have other issues IMO. I've heard more horror stories of HR lifters spinning at 6000RPM than Solids.
They have their advantages more aggressive cam, higher RPM and more power. But they need a litte bit of maintenance. I don't believe they are necessary on all builds and if you don't need them I wouldn't use them, but I would not be afraid of them.

I was afraid of them when JimV bought solid cams for my original builds 7yrs ago. I actually really like them now.

Its only turning 5300-5500 RPMS

Solid lifters would be a waste of money in your situation. The high rpm morel hydraulic lifters are good for 7300 rpm and like lots of spring pressure. Why put a time bomb in your motor?

With the hydraulic morel lifters on the market today, I just don't see a good enough reason to warrant a solid roller. 15 years ago, absolutely. The new morel lifters are more than capable. The margin on power between the two camshafts has been narrowed also.

so now I'm thinking the next best thing would be the Short travel lifters? Any thoughts or should I just stay with my standard retro-Hydraulic roller lifters?

Imo the stock 502 roller lifter is plenty good for 5500 rpm, I use them and pull my motors to 6000, with a radical cam, I believe the key is a properly matched set of valve springs. Again just my opinion. It seems to work for me.

Short travel lifters are ment for certain class type drag racing where a hydraulic lifter must be used. They usually run them on a solid lifter camshaft with 0 to .012 lash which is a big no no in a boat. They will get beat to death. The Comp limited travel lifters are total junk and usually don't make it past a few start ups. The Morel limited travel lifters are very nice pieces. The Morel limited travel and the high rpm lifters use the same lifter bodies but have less travel. The only way to tell the Morels apart is by taking them apart. If you are only gonna spin the motor to 6000 a standard Morel lifter would be fine I think they are good for either 6300 or 6500 can't remember. The rpms are rated for 7300 and I know of someone running them on a dyno past 7500rpm and still not collapsing. I don't the you would ever spin a boat motor past 7500.