Are tantalums good for PIC Vcap?
The PIC's datasheet says less than 1 Ohm ESR and it specifically mentions tantalum as being OK.


  The regulator provides power to the core from the other VDD pins. A
  low-ESR (less than 1 Ohm) capacitor (such as tantalum or ceramic) must
  be connected to the VCAP pin (Figure 27-1). This helps to maintain the
  stability of the regulator. The recommended value for the filter
  capacitor is provided in Table 30-5 located in Section 30.0
  “Electrical Characteristics”.


http://www.avx.com/docs/Catalogs/techsum.pdf

Has a lot of information about tantalum capacitor failure modes.  It's an interesting read.

Steady-State


  Tantalum Dielectric has essentially no wear out mechanism and in
  certain circumstances is capable of limited self healing. However,
  random failures can occur in operation. The failure rate of Tantalum
  capacitors will decrease with time and not increase as with other
  electrolytic capacitors and other electronic components.


IMO tantalum are fine for this application. I wouldn't be concerned about age unless you have some very special requirements.