Neither of mine were staked, but I only have the 1905 (Type 38) and a Siamese from the 1920s, so that's no indication as to the 99 Shiki.
If it were my rifle, I really think I would disassemble it because you never know what could be lurking under the wood. Big tarantulas, jungle-rot, dry-rot in the woodwork, (shudder!!) RUST on the metal.... anything could be there.
For pure prevention, I would disassemble carefully, reserving for myself the thrill in the knowledge that I am the first person who didn't drink sake ever to see the inside of this rifle.
As to your Lee-Enfield junk, I CAN'T buy it because the Old Farts' Pension doesn't come in for another 2 weeks!! Otherwise I would, and that's serious.