Olaf the Stout said:
13th level is probably ok as it won't totally dominate a combat and gives the wizard/sorcerer/whatever a "back-up" spell that never runs out.
Do you have to recharge the staff though?
Nope. Most of its abilities are "1/day" or "3/day", although there are a few constant abilities (read magic, scorching ray) as noted.
I'm pretty certain that my group doesn't browse EN World much, so here's the full Staff of Dragon's Tears:
5th: 3/day-magic missile
6th: (lose 1st level slot) At will-detect magic, read magic, arcane mark
7th: (-1 all saves; -1 caster level) -
8th: (-1 all skills; lose 2nd level slot) +2 enhancement bonus to Intelligence or Charisma
9th: 3/day - Lesser Enlarge Spell
10th: (lose 3rd level slot); +5 competence bonus to Spellcraft checks
11th: 3/day - Lesser Empower Spell
12th: (lose 4th level slot); at will -
scorching ray
13th: 1/day -
fireball
14th: (lose 5th level slot); +4 enhancement bonus to Intelligence or Charisma
15th: (-2 to caster level); Darkvision 60 ft.
16th: (lose 6th level slot); 3/day - Extend Spell
17th: +6 enhancement to Intelligence or Charisma;
see invisibility
18th: (lose 7th level slot); 3/day - Greater Enlarge Spell
19th: 3/day - Lesser Quicken Spell
20th: (lose 8th level slot); 3/day - Empower Spell
Legacy Rituals:
Least (3,500 gp): Travel to a shrine of Corellon Larethian and ask the blessing of the god of the elves.
Lesser (13,500 gp): Engage in research of the planes and arcane magic at a greater library.
Greater (43,000 gp): Stand in judgement before one of the seven Gold Dragons who serve Bahamut.
Note: all penalties are non-cumulative in this case; at 18th level, Peggy has -2 to all skills, -1 to all saves, -1 to caster level and has lost one 7th level slot. Assuming I've copied them down correctly, of course!
Cheers!